aries | p1: zsmalloc: fixup trivial zs size classes value in comments

According to calculation, ZS_SIZE_CLASSES value is 255 on systems with 4K
page size, not 254.  The old value may forget count the ZS_MIN_ALLOC_SIZE
in.

This patch fixes this trivial issue in the comments.

Signed-off-by: Weijie Yang <weijie.yang@samsung.com>
Cc: Minchan Kim <minchan@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Humberto Borba <humberos@gmail.com>

Change-Id: Ib735c9a470c629f3fa9b2662036b77d3fd4315d3