regmap: Add helper function for checking if a register range is volatile
regmap: Add helper function for checking if a register range is volatile

We already have the same code for checking whether a register range is volatile
in two different places. Instead of duplicating it once more  add a small helper
function for checking whether a register range is voltaile.

Signed-off-by: Lars-Peter Clausen <3318dc5ce3e4fb7c28a0b841b6801c884e1d0896@metafoo.de>
Signed-off-by: Mark Brown <b51b9a92386687a9ac927cebfa0f978adeb8cea5@opensource.wolfsonmicro.com>

KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs