Fix undefined behavior in definition of hsa_amd_memory_fault_reason_t

Currently, the definition of hsa_amd_memory_fault_reason_t tries to
set a constant of 0x8000_0000 by using the definition "1 << 31".

However, the 1 in this definition is a signed integer by C++ rules.
On our architectures, shifting a signed integer by 31 results in
signed integer overflow. Signed integer overflow results in
undefined behavior.

Forcing the 1 to be unsigned avoids this.

Change-Id: I860431eeede4eff29598f646abf3c1337b048d71

runtime/hsa-runtime/inc/hsa_ext_amd.h

@@ -2296,7 +2296,7 @@ typedef enum {
   // SRAM ECC failure (ie registers, no fault address).
   HSA_AMD_MEMORY_FAULT_SRAMECC = 1 << 6,
   // GPU reset following unspecified hang.
-  HSA_AMD_MEMORY_FAULT_HANG = 1 << 31
+  HSA_AMD_MEMORY_FAULT_HANG = 1U << 31
 } hsa_amd_memory_fault_reason_t;
 
 /**