regmap: Support bulk writes for devices without raw formatting

When doing a bulk writes from a device which lacks raw I/O support we
fall back to doing register at a time reads but we still use the raw
formatters in order to render the data into the word size used by the
device (since bulk reads still operate on the device word size rather
than unsigned ints).  This means that devices without raw formatting
such as those that provide reg_read() are not supported.  Provide
handling for them by copying the values read into native endian values
of the appropriate size.

This complements commit d5b98eb1

 ("regmap: Support bulk reads for
devices without raw formatting").

Signed-off-by: Chen-Yu Tsai <wens@csie.org>
Signed-off-by: Mark Brown <broonie@kernel.org>