extcon: max77693: Fix bug of build error related to INPUT subsystem

This patch fix build error of following log:

drivers/built-in.o: In function `max77693_muic_remove':
extcon-max77693.c:(.text+0x664853): undefined reference to `input_unregister_device'
drivers/built-in.o: In function `max77693_muic_probe':
extcon-max77693.c:(.text+0x664971): undefined reference to `input_allocate_device'
extcon-max77693.c:(.text+0x6649c1): undefined reference to `input_set_capability'
extcon-max77693.c:(.text+0x6649d6): undefined reference to `input_set_capability'
extcon-max77693.c:(.text+0x6649eb): undefined reference to `input_set_capability'
extcon-max77693.c:(.text+0x664a00): undefined reference to `input_set_capability'
extcon-max77693.c:(.text+0x664a15): undefined reference to `input_set_capability'
extcon-max77693.c:(.text+0x664a20): undefined reference to `input_register_device'
drivers/built-in.o: In function `max77693_muic_adc_handler':
extcon-max77693.c:(.text+0x665318): undefined reference to `input_event'
extcon-max77693.c:(.text+0x66532a): undefined reference to `input_event'
make[1]: *** [vmlinux] Error 1

Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>
Signed-off-by: Myungjoo Ham <myungjoo.ham@samsung.com>
Reported-by: Randy Dunlap <rdunlap@infradead.org>
Acked-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>