selftests/powerpc: Skip 4PB test on 4K PAGE_SIZE systems

Systems using the hash MMU with a 4K page size don't support 4PB address
space, so skip the test because the bug it tests for can't be triggered.
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20220901020215.254097-1-mpe@ellerman.id.au

tools/testing/selftests/powerpc/mm/large_vm_gpr_corruption.c

@@ -112,6 +112,8 @@ static int test(void)
 	// This tests a hash MMU specific bug.
 	FAIL_IF(using_hash_mmu(&hash_mmu));
 	SKIP_IF(!hash_mmu);
+	// 4K kernels don't support 4PB address space
+	SKIP_IF(sysconf(_SC_PAGESIZE) < 65536);
 
 	page_size = sysconf(_SC_PAGESIZE);