pinctrl: palmas: PINCTRL_PALMAS needs to select PINMUX

Fix below build error if !PINMUX.

  CC      drivers/pinctrl/pinctrl-palmas.o
drivers/pinctrl/pinctrl-palmas.c:741:21: error: variable 'palmas_pinmux_ops' has initializer but incomplete type
drivers/pinctrl/pinctrl-palmas.c:742:2: error: unknown field 'get_functions_count' specified in initializer
drivers/pinctrl/pinctrl-palmas.c:742:2: warning: excess elements in struct initializer [enabled by default]
drivers/pinctrl/pinctrl-palmas.c:742:2: warning: (near initialization for 'palmas_pinmux_ops') [enabled by default]
drivers/pinctrl/pinctrl-palmas.c:743:2: error: unknown field 'get_function_name' specified in initializer
drivers/pinctrl/pinctrl-palmas.c:743:2: warning: excess elements in struct initializer [enabled by default]
drivers/pinctrl/pinctrl-palmas.c:743:2: warning: (near initialization for 'palmas_pinmux_ops') [enabled by default]
drivers/pinctrl/pinctrl-palmas.c:744:2: error: unknown field 'get_function_groups' specified in initializer
drivers/pinctrl/pinctrl-palmas.c:744:2: warning: excess elements in struct initializer [enabled by default]
drivers/pinctrl/pinctrl-palmas.c:744:2: warning: (near initialization for 'palmas_pinmux_ops') [enabled by default]
drivers/pinctrl/pinctrl-palmas.c:745:2: error: unknown field 'enable' specified in initializer
drivers/pinctrl/pinctrl-palmas.c:745:2: warning: excess elements in struct initializer [enabled by default]
drivers/pinctrl/pinctrl-palmas.c:745:2: warning: (near initialization for 'palmas_pinmux_ops') [enabled by default]
make[2]: *** [drivers/pinctrl/pinctrl-palmas.o] Error 1
make[1]: *** [drivers/pinctrl] Error 2
make: *** [drivers] Error 2

Signed-off-by: Axel Lin <axel.lin@ingics.com>
Acked-by: Laxman Dewangan <ldewangan@nvidia.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>