x86/fpu: Rename restore_fpu_checking() to copy_fpstate_to_fpregs()

fpu_restore_checking() is a helper function of restore_fpu_checking(),
but this is not apparent from the naming.

Both copy fpstate contents to fpregs, while the fuller variant does
a full copy without leaking information.

So rename them to:

    copy_fpstate_to_fpregs()
  __copy_fpstate_to_fpregs()

Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>