mfd: palmas: Add SMPS10_BOOST feature

The SMPS10 regulator is not presesnt in all the variants
of the PALMAS PMIC family. Hence adding a feature to distingush
between them.

Signed-off-by: J Keerthy <j-keerthy@ti.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>