drivers/rtc/rtc-pxa.c: avoid cpuid checking

pxa-rtc is widely used in pxa27x/pxa3xx/pxa93x/pxa95x. Checking cpuid in
pxa-rtc driver is unnecessary since we assign on-chip device in soc files.

Signed-off-by: Haojian Zhuang <haojian.zhuang@marvell.com>
Cc: Alessandro Zummo <a.zummo@towertech.it>
Cc: Grant Likely <grant.likely@secretlab.ca>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>