pwm: stmpe: Fix wrong register offset for hwpwm=2 case

[ Upstream commit 8472b529e113e0863ea064fdee51bf73c3f86fd6 ]

Fix trivial copy/paste bug.

Signed-off-by: Axel Lin <axel.lin@ingics.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Fixes: ef1f09ec ("pwm: Add a driver for the STMPE PWM")
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>