pxa: fix previous definition on cpu init

start.S:183:1: warning: "ICMR" redefined
In file included from start.S:33:
include/asm/arch/pxa-regs.h:935:1: warning: this is the location of the previous definition
start.S:187:1: warning: "RCSR" redefined
...

Signed-off-by: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>