mfd: palmas: Add support of module build for Ti palmas chip

Modified Kconfig to enable module build support

Signed-off-by: Guillaume La Roque <glaroque@baylibre.com>
Signed-off-by: Nicolas Frayer <nfrayer@baylibre.com>
Signed-off-by: Lee Jones <lee@kernel.org>
Link: https://lore.kernel.org/r/20221026140911.204776-1-nfrayer@baylibre.com