minidump: Add support for !CONFIG_SMP kernel

__per_cpu variables are only applicable for the systems with multiple cpu
Minidump code without any check for same was causing the kernel compilation
to fail for the single core cpu where __per_cpu symbols are not applicable
so added conditional compilation to the __per_cpu code based on CONFIG_SMP.

Change-Id: I626fc3c47fd9600608ea721ef6f8811110e1ee1d
Signed-off-by: Deepak Dimri <ddimri@codeaurora.org>