selftests: proc: remove unreached code and fix build warning

selftests: proc: remove unreached code and fix build warning

fix the following warning:
proc-empty-vm.c:385:17: warning: ignoring return value of `write'
 declared with attribute `warn_unused_result' [-Wunused-result]
  385 |                 write(1, buf, rv);
      |                 ^~~~~~~~~~~~~~~~~

Link: https://lkml.kernel.org/r/20240603124220.33778-1-amer.shanawany@gmail.com
Signed-off-by: Amer Al Shanawany <amer.shanawany@gmail.com>
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/r/202404010211.ygidvMwa-lkp@intel.com/
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Javier Carrasco <javier.carrasco.cruz@gmail.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Swarup Laxman Kotiaklapudi <swarupkotikalapudi@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>