msm: idle: fix pm-boot driver compilation errors

CONFIG_CPU_V7 is not defined for latest ARM based targets.
Due to this few variables and function definitions are not
visible to driver and this causes the driver compilation
failure(pm-boot.c).

Change-Id: I823bd14bd992bae5d079fddc6b717869c79e102e
Signed-off-by: Murali Nalajala <mnalajal@codeaurora.org>