Split regmap_get_endian() in two functions, regmap_get_reg_endian() and
regmap_get_val_endian().
This allows to:
- Get rid of the three switch()es on "type", incl. error handling in
three "default" cases,
- Get rid of the regmap_endian_type enum,
- Get rid of the non-NULL check of "config" (regmap_init() already
checks for that),
- Get rid of the "endian" output parameters, and just return the
regmap_endian enum value, as the functions can no longer fail.
This saves 21 lines of code (despite the still-present
one-comment-per-line over-documentation), and 30 bytes of code on ARM
V7.