reset: Mark function as static and remove unused function in core.c

Mark function of_reset_simple_xlate() as static in core.c
because it is not used outside this file.
Also, remove functions devm_reset_control_put() and
devm_reset_control_match() because they are unused.

This eliminates the following warnings in core.c:
drivers/reset/core.c:46:5: warning: no previous prototype for ‘of_reset_simple_xlate’ [-Wmissing-prototypes]
drivers/reset/core.c:262:6: warning: no previous prototype for ‘devm_reset_control_put’ [-Wmissing-prototypes]

Signed-off-by: Rashika Kheria <rashika.kheria@gmail.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>