mfd: Enabling twl4030_wdt and pwrbutton only for Triton

Enabling twl4030_wdt and twl4030_pwrbutton only for Triton i.e for
TWL4030 and TWL5030. This is to be excluded for Phoenix TWL6030.
Tested OMAP4 blaze, OMAP2430, OMAP3630 boot up.

Signed-off-by: Keerthy <j-keerthy@ti.com>
Reviewed-by: Balaji T K <balajitk@ti.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>