paride: fix up build warning on mips platforms

MIPS include files define "PC" so when building the paride driver the
following build warning shows up:

rivers/block/paride/bpck.c:32: warning: "PC" redefined

Fix this by undefining PC before redefining it as is done for other
defines in this driver.

Cc: Tim Waugh <[e-mail]>
Acked-by: Jens Axboe <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/block/paride/bpck.c

···
 
 #undef r2
 #undef w2
+#undef PC
 
 #define PC			pi->private
 #define r2()			(PC=(in_p(2) & 0xff))