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.

Additionally, this feature also exposes the number of successful CMA
pages that have been freed. This can be used with the number of CMA
pages that have been successfully allocated to deduce how many CMA
pages are allocated at a particular moment in time.

This is useful, as it provides some insight into how memory is
allocated, therefore allowing Android to improve its lost RAM
calculation.

Bug: 179256052
Bug: 371518137
Bug: 228238851
Signed-off-by: Minchan Kim <minchan@google.com>
Change-Id: I5c8dc58a5d195d2e1b2e25628545f7d2a9c3b7df
Signed-off-by: Richard Chang <richardycc@google.com>
[isaacmanjarres: added additional bug tags and expanded commit
message.]
Signed-off-by: Isaac J. Manjarres <isaacmanjarres@google.com>