pwm: rzg2l-gpt: Allow checking period_tick cache value only if sibling channel is...

pwm: rzg2l-gpt: Allow checking period_tick cache value only if sibling channel is enabled

The rzg2l_gpt_config() tests the rzg2l_gpt->period_tick variable when
both channels of a hardware channel are in use. This check is not valid
if rzg2l_gpt_config() is called after disabling all the channels, as it
tests against the cached value. Hence, allow checking and setting the
cached value only if the sibling channel is enabled.

While at it, drop else after return statement to fix the check patch
warning.

Cc: stable@kernel.org
Fixes: 061f087f5d0b ("pwm: Add support for RZ/G2L GPT")
Signed-off-by: Biju Das <biju.das.jz@bp.renesas.com>
Link: https://patch.msgid.link/20251126104308.142302-1-biju.das.jz@bp.renesas.com
Signed-off-by: Uwe Kleine-König <ukleinek@kernel.org>