[pwm, rtl] PWM RTL update to fix a lint error
[pwm, rtl] PWM RTL update to fix a lint error

  - Update the pwm_core.sv file to fix a lint error

Signed-off-by: Muqing Liu <b1c0f8d5c8fd5df55dfdf439926eb15b5e395e02@wdc.com>

lowRISC/opentitan,lowRISC/opentitan,lowRISC/opentitan,lowRISC/opentitan,lowRISC/opentitan,lowRISC/opentitan