ANDROID: inline isolate_and_split_free_page

Add inline keyword to pass compilation when CONFIG_COMPACTION is not
enabled.

include/linux/compaction.h:241:22: warning: 'isolate_and_split_free_page' defined but not used [-Wunused-function]

Bug: 175403896
Change-Id: I6bec2789a68e1b8fc9f4ea8f7267571a333d68ef
Fixes: 061e34c5 ("ANDROID: mm: compaction: fix isolate_and_split_free_page() redefinition")
Signed-off-by: Elliot Berman <eberman@codeaurora.org>
(cherry picked from commit b9836d40)
Signed-off-by: Sukadev Bhattiprolu <quic_sukadev@quicinc.com>