Input: fix PWM-related undefined reference errors

This patch adds a PWM dependency to configure the INPUT_MAX8997_HAPTIC
and INPUT_PWM_BEEPER. Without this patch, build system can lead to build
failure. This was observed during randconfig testing, in which
INPUT_MAX8997_HAPTIC or INPUT_PWM_BEEPER was enabled w/o PWM being
enabled, leading to the following errors:

init/built-in.o
drivers/built-in.o: In function `max8997_haptic_disable':
:(.text+0x1073a0): undefined reference to `pwm_disable'
drivers/built-in.o: In function `max8997_haptic_remove':
:(.text+0x1073fc): undefined reference to `pwm_free'
drivers/built-in.o: In function `max8997_haptic_play_effect_work':
:(.text+0x1074f0): undefined reference to `pwm_config'
:(.text+0x1075b0): undefined reference to `pwm_enable'
drivers/built-in.o: In function `max8997_haptic_probe':
:(.text+0x1076f8): undefined reference to `pwm_request'
:(.text+0x1077e8): undefined reference to `pwm_free'
drivers/built-in.o: In function `pwm_beeper_resume':
:(.text+0x1081a4): undefined reference to `pwm_config'
make: *** [vmlinux] Error 1

Signed-off-by: Manjunath Goudar <csmanjuvijay@gmail.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>