selftests/x86/pkeys: Remove unused functions

selftests/x86/pkeys: Remove unused functions

This also gets rid of two build warnings:

  protection_keys.c: In function ‘dumpit’:
  protection_keys.c:419:3: warning: ignoring return value of ‘write’, declared with attribute warn_unused_result [-Wunused-result]
     write(1, buf, nr_read);
     ^~~~~~~~~~~~~~~~~~~~~~

Cc: Linus Torvalds <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: Shuah Khan <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: [email protected]
Signed-off-by: Ingo Molnar <[email protected]>