regmap: Factor range lookup out of page selection
regmap: Factor range lookup out of page selection

This will support a subsequent update to allow bulk writes to cross window
boundaries.

Signed-off-by: Mark Brown <b51b9a92386687a9ac927cebfa0f978adeb8cea5@opensource.wolfsonmicro.com>

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