x86: Clean up various simple wrapper functions

Remove unneeded variables and assignments.

While we are here, let's fix the following as well:

  - Remove unnecessary parentheses
  - Remove unnecessary unsigned-suffix 'U' from constant values
  - Reword the comment in set_apic_id() (suggested by Thomas Gleixner)

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: Alex Thorlton <athorlton@sgi.com>
Cc: Andrew Banman <abanman@sgi.com>
Cc: Borislav Petkov <bp@suse.de>
Cc: Daniel J Blueman <daniel@numascale.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Dimitri Sivanich <sivanich@sgi.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Matt Fleming <matt@codeblueprint.co.uk>
Cc: Mike Travis <travis@sgi.com>
Cc: Nathan Zimmer <nzimmer@sgi.com>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steffen Persvold <sp@numascale.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Toshi Kani <toshi.kani@hpe.com>
Cc: Wei Jiangang <weijg.fnst@cn.fujitsu.com>
Link: http://lkml.kernel.org/r/1473573502-27954-1-git-send-email-yamada.masahiro@socionext.com


Signed-off-by: Ingo Molnar <mingo@kernel.org>