[Offload] XFAIL four tests while working on fix (#98899)

omp_dynamic_shared_memory_mixed_amdgpu.c
omp_dynamic_shared_memory_amdgpu.c
amdgcn-amd-amdhsa::bug51982.c
amdgcn-amd-amdhsa::bug51781.c

Author: jplehr

offload/test/api/omp_dynamic_shared_memory_amdgpu.c

@@ -2,6 +2,7 @@
 // RUN: env LIBOMPTARGET_SHARED_MEMORY_SIZE=256 \
 // RUN:   %libomptarget-run-amdgcn-amd-amdhsa | %fcheck-amdgcn-amd-amdhsa
 // REQUIRES: amdgcn-amd-amdhsa
+// XFAIL: amdgcn-amd-amdhsa
 
 #include <omp.h>
 #include <stdio.h>

offload/test/api/omp_dynamic_shared_memory_mixed_amdgpu.c

@@ -2,6 +2,7 @@
 // RUN: env LIBOMPTARGET_NEXTGEN_PLUGINS=1 \
 // RUN:   %libomptarget-run-amdgcn-amd-amdhsa | %fcheck-amdgcn-amd-amdhsa
 // REQUIRES: amdgcn-amd-amdhsa
+// XFAIL: amdgcn-amd-amdhsa
 
 #include "omp_dynamic_shared_memory_mixed.inc"
 // CHECK: PASS

offload/test/offloading/bug51781.c

@@ -31,6 +31,7 @@
 // RUN: %libomptarget-run-generic 2>&1 | %fcheck-generic
 //
 // CUSTOM: Rewriting generic-mode kernel with a customized state machine.
+// XFAIL: amdgcn-amd-amdhsa
 
 #if ADD_REDUCTION
 #define REDUCTION(...) reduction(__VA_ARGS__)

offload/test/offloading/bug51982.c

@@ -1,6 +1,7 @@
 // RUN: %libomptarget-compile-generic -O1 && %libomptarget-run-generic
 // -O1 to run openmp-opt
 // RUN: %libomptarget-compileopt-generic -O1 && %libomptarget-run-generic
+// XFAIL: amdgcn-amd-amdhsa
 
 int main(void) {
   long int aa = 0;