Use i8253.c lock for PC speaker on MIPS, too.

The Jazz machines have to use the PIT timer for dyntick and highresolution
kernels.  This may break because currently just like i386 used to do MIPS
uses two separate spinlocks in the actual PIT code and the PC speaker
code.  So switch to do it the same that x86 currently does PIT locking.

Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>