corrected offline kernel compilation on hipcc path

1. hipgenisa.sh now adds int main(){} during kernel compilation. User does not have to put it there
2. Renamed vcpy_isa.cpp to vcpy_kernel.cpp
3. Removed vcpy_isa.cu as the kernel code should be common for both paths
4. Changed Makefile and runkernel.cpp to work with above changes

Change-Id: I9f8c84706b44bb500bc493a68e959762b55a0142

samples/0_Intro/module_api/vcpy_kernel.cpp

@@ -0,0 +1,8 @@
+#include<hip_runtime.h>
+
+__global__ void hello_world(hipLaunchParm lp, float *a, float *b)
+{
+    int tx = hipThreadIdx_x;
+    b[tx] = a[tx];
+}
+