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

drivers/mfd/Kconfig

@@ -1489,7 +1489,7 @@ config MFD_OMAP_USB_HOST
 	  OMAP USB Host drivers.
 
 config MFD_PALMAS
-	bool "TI Palmas series chips"
+	tristate "TI Palmas series chips"
 	select MFD_CORE
 	select REGMAP_I2C
 	select REGMAP_IRQ