x86/tsc: Remove redundant assignment

Previously, the assignment to the local variable 'now' took place
before the for loop. The loop is unconditional so it will be entered
at least once. The variable 'now' is reassigned in the loop and is not
used before reassigning. Therefore, the assignment before the loop is
unnecessary and can be removed.

No code changed:

  # arch/x86/kernel/tsc_sync.o:

   text    data     bss     dec     hex filename
   3569     198      44    3811     ee3 tsc_sync.o.before
   3569     198      44    3811     ee3 tsc_sync.o.after

md5:
   36216de29b208edbcd34fed9fe7f7b69  tsc_sync.o.before.asm
   36216de29b208edbcd34fed9fe7f7b69  tsc_sync.o.after.asm

 [ bp: Massage commit message. ]

Signed-off-by: Mateusz Nosek <mateusznosek0@gmail.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20200118171143.25178-1-mateusznosek0@gmail.com