pwm: lpc18xx-sct: Drop driver local locking

pwm: lpc18xx-sct: Drop driver local locking

Both mutexes are only used in one function each. These functions are only
called by the .apply() callback. As the .apply() calls are serialized by
the core since commit 1cc2e1faafb3 ("pwm: Add more locking") the mutexes
have no effect apart from runtime overhead. Drop them.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@baylibre.com>
Reviewed-by: Vladimir Zapolskiy <vz@mleia.com>
Link: https://lore.kernel.org/r/4f7a2da37adbfe4743564245119045826d86eca6.1750788649.git.u.kleine-koenig@baylibre.com
Signed-off-by: Uwe Kleine-König <ukleinek@kernel.org>