kfdtest: Take vram size into account when calculate buffer number.

Vram size is relatively smaller in APU, e.g. 512MB.
Current MMBench doesn't support small vram system.
Running MMBench may have below errors:

[ RUN      ] KFDMemoryTest.MMBench
[          ] Found VRAM of 512MB.
[          ] Test (avg. ns)        alloc   mapOne  umapOne   mapAll  umapAll     free
[          ] --------------------------------------------------------------------------
[          ]   4K-SysMem-noSDMA         4569    20098     1292    18835      926     2218
[          ]  64K-SysMem-noSDMA        12738    20469     1030    19201     1293     4560
[          ]   2M-SysMem-noSDMA       256384    21020     1022    20568     1196    36294
[          ]  32M-SysMem-noSDMA      4031812    83750     5406    61156     4312   535656
[          ]   1G-SysMem-noSDMA    129260000   427000    34000   390000    30000 18548000
[          ] --------------------------------------------------------------------------
[          ]   4K-VRAM-noSDMA         3594    19637      979    19624     1357     2829
[          ]  64K-VRAM-noSDMA         3540    21062     1407    19614     1654     3024
/home/foreman/build/hsakmt-roct-amdgpu-1.0.9/sources/libhsakmt/tests/kfdtest/src/KFDMemoryTest.cpp:1119: Failure
Value of: (hsaKmtAllocMemory(allocNode, bufSize, memFlags, &bufs[i]))
  Actual: 6
Expected: HSAKMT_STATUS_SUCCESS
Which is: 0
[  FAILED  ] KFDMemoryTest.MMBench (723 ms)

Fix this issue by changing buffer number calculation in MMBench.

Change-Id: I5cce95707a048248f1e825c807586818619eddaf
Signed-off-by: Yifan Zhang <yifan1.zhang@amd.com>

tests/kfdtest/src/KFDMemoryTest.cpp

@@ -1099,6 +1099,7 @@ TEST_F(KFDMemoryTest, MMBench) {
         unsigned nBufs = TEST_NBUFS(testIndex);
         unsigned memType = TEST_MEMTYPE(testIndex);
         bool interleaveSDMA = TEST_SDMA(testIndex);
+        unsigned bufLimit;
         HSAuint64 allocTime, map1Time, unmap1Time, mapAllTime, unmapAllTime, freeTime;
         HSAuint32 allocNode;
 
@@ -1119,6 +1120,13 @@ TEST_F(KFDMemoryTest, MMBench) {
             memFlags.ui32.PageSize = HSA_PAGE_SIZE_4KB;
             memFlags.ui32.HostAccess = 0;
             memFlags.ui32.NonPaged = 1;
+            /* Upper limit of buffer number to fit 90% vram size */
+            bufLimit = ((vramSizeMB << 20) * 9 / 10) / bufSize ;
+            if (bufLimit == 0)
+                continue; // skip when bufSize > vram
+
+            /* When vram is too small to fit all the buffers, fill 90% vram size*/
+            nBufs = (nBufs < bufLimit) ? nBufs : bufLimit;
         }
 
         /* Allocation */