staging: regulator: hi6421v600-regulator: port it to upstream

The driver was originally written for Kernel 4.9. It needs to
be ported to upstream:

	- Got rid of timeval;
	- Removed a bogus dependency;
	- Did cleanups at the header file.

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Link: https://lore.kernel.org/r/9e34400d2cc15ef501a8478f69a95c9abc5c4d8d.1597647359.git.mchehab+huawei@kernel.org


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>