PWMs on PXA168/910 start at number 1 instead of 0, (i.e. PWM1/2/3/4 instead
of PWM0/1/2/3 on PXA25x/PXA27x/PXA3xx). Allow this number to be specified
in pwm_id_table.
Signed-off-by: Eric Miao <eric.miao@marvell.com>