tools: fix -Wunused-result in linux.c

tools: fix -Wunused-result in linux.c

Fix the following -Wunused-result warnings on posix_memalign()
return values and add error handling.

./shared/linux.c:100:25: warning: ignoring return value of `posix_memalign' declared with attribute `warn_unused_result' [-Wunused-result]
  100 |          posix_memalign(&p, cachep->align, cachep->size);
      |          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
../shared/linux.c: In function `kmem_cache_alloc_bulk':
../shared/linux.c:198:33: warning: ignoring return value of `posix_memalign' declared with attribute `warn_unused_result' [-Wunused-result]
  198 |          posix_memalign(&p[i], cachep->align,
      |          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  199 |                                cachep->size);
      |                                ~~~~~~~~~~~~~

Link: https://lkml.kernel.org/r/20241011225155.27607-1-skhan@linuxfoundation.org
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>
Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Reviewed-by: Liam R. Howlett <Liam.Howlett@Oracle.com>
Cc: Sidhartha Kumar <sidhartha.kumar@oracle.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>