Merge 4.19.315 into android-4.19-stable

Changes in 4.19.315
	Revert "selftests: mm: fix map_hugetlb failure on 64K page size systems"
	dm: limit the number of targets and parameter size area
	btrfs: add missing mutex_unlock in btrfs_relocate_sys_chunks()
	tracing: Simplify creation and deletion of synthetic events
	tracing: Add unified dynamic event framework
	tracing: Use dyn_event framework for synthetic events
	tracing: Remove unneeded synth_event_mutex
	tracing: Consolidate trace_add/remove_event_call back to the nolock functions
	string.h: Add str_has_prefix() helper function
	tracing: Use str_has_prefix() helper for histogram code
	tracing: Use str_has_prefix() instead of using fixed sizes
	tracing: Have the historgram use the result of str_has_prefix() for len of prefix
	tracing: Refactor hist trigger action code
	tracing: Split up onmatch action data
	tracing: Generalize hist trigger onmax and save action
	tracing: Remove unnecessary var_ref destroy in track_data_destroy()
	serial: kgdboc: Fix NMI-safety problems from keyboard reset code
	docs: kernel_include.py: Cope with docutils 0.21
	Linux 4.19.315

Change-Id: I20fdf3ecd83c6f7654e6118390444de784a0b100
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>