ANDROID: GKI: enable CONFIG_CMA_SYSFS

Since CMA is getting used more widely, it's more important to
keep monitoring CMA statistics for system health since it's
directly related to user experience.

This feature introduces sysfs statistics for CMA, in order to provide
some basic monitoring of the CMA allocator.

     * the number of CMA page successful allocations
     * the number of CMA page allocation failures

These two values allow the user to calculate the allocation
failure rate for each CMA area.

Bug: 179256052
Signed-off-by: Minchan Kim <minchan@google.com>
Change-Id: I5c8dc58a5d195d2e1b2e25628545f7d2a9c3b7df
Signed-off-by: Richard Chang <richardycc@google.com>
(cherry picked from commit f45afb45)