Kconfig: Add config option to support vmalloc savings

The virtual space belonging to any subsystem which is
expected to have a lifetime of the entire system can be
reclaimed. Adding config option to enable or disable
this feature.

Change-Id: I56faef4b71c948185fdfe336054a5951dfa8d011
Signed-off-by: Neeti Desai <neetid@codeaurora.org>