x86: microcode: fix sparse warnings

Impact: make global variables and a function static

Fix following sparse warnings:

  arch/x86/kernel/microcode_core.c:102:22: warning: symbol
  'microcode_ops' was not declared. Should it be static?
  arch/x86/kernel/microcode_core.c:206:24: warning: symbol
  'microcode_pdev' was not declared. Should it be static?
  arch/x86/kernel/microcode_core.c:322:6: warning: symbol
  'microcode_update_cpu' was not declared. Should it be static?
  arch/x86/kernel/microcode_intel.c:468:22: warning: symbol
  'microcode_intel_ops' was not declared. Should it be static?

Signed-off-by: Hannes Eder <hannes@hanneseder.net>
Signed-off-by: Ingo Molnar <mingo@elte.hu>