serial: 8250_bcm2835aux: Fix clock imbalance in PM resume

serial: 8250_bcm2835aux: Fix clock imbalance in PM resume

During review Ulf Hansson discovered a clock imbalance in the recently
introduced PM resume code. The driver should enable the clock only in
case it has been disabled in suspend before. In order to make the
conditions easier to read, refactor this into a separate function.

Reported-by: Ulf Hansson <ulf.hansson@linaro.org>
Closes: https://lore.kernel.org/linux-arm-kernel/CAPDyKFoJh3j8xSeXZ9o031YZLTCDYVA+dgvURuwozjDpU_aauA@mail.gmail.com/
Fixes: 0e1d8780526f ("serial: 8250_bcm2835aux: add PM suspend/resume support")
Signed-off-by: Stefan Wahren <wahrenst@gmx.net>
Link: https://lore.kernel.org/r/20240818174936.88372-1-wahrenst@gmx.net
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>