Input: pm8941-pwrkey - fix dev_dbg() output in pm8941_pwrkey_irq()

Input: pm8941-pwrkey - fix dev_dbg() output in pm8941_pwrkey_irq()

Since 'sw_debounce_end_time' of 'struct pm8941_pwrkey' is of type
'ktime_t', use 'ktime_to_us()' to print the value in microseconds
as it is announced in a call to 'dev_dbg()'. Compile tested only.

Fixes: 0b65118e6ba3 ("Input: pm8941-pwrkey - add software key press debouncing support")
Signed-off-by: Dmitry Antipov <dmantipov@yandex.ru>
Reviewed-by: David Collins <quic_collinsd@quicinc.com>
Link: https://lore.kernel.org/r/20250216170336.861025-1-dmantipov@yandex.ru
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>