Change type of cpsr in arm_sigreturn_next_pc

Variable cpsr holds the value of cpsr register, which is 32-bit.  It
is better to explicitly use uint32_t.

gdb/gdbserver:

2016-05-05  Yao Qi  <yao.qi@linaro.org>

	* linux-arm-low.c (arm_sigreturn_next_pc): Change type of cpsr
	to uint32_t.