mm/vmalloc.c: Correctly calculate VMALLOC_TOTAL

VMALLOC_TOTAL currently only accounts for the 'official' vmalloc
region when CONFIG_ENABLE_VMALLOC_SAVING is enabled. Account for all
regions when the config is enabled.

Change-Id: I7b977b050b5c0c1a69a94e876389ba8c5711432b
Signed-off-by: Laura Abbott <lauraa@codeaurora.org>