regulator: mp5416: remove kernel.h include

Driver does not seem to utilize anything from the kernel.h, compiles
and works fine for me without it.

So remove kernel.h include as it pulls in a lot of unused stuff.

Signed-off-by: Robert Marko <robimarko@gmail.com>
Cc: christophe.jaillet@wanadoo.fr
Link: https://lore.kernel.org/r/20220607124759.775133-1-robimarko@gmail.com


Signed-off-by: Mark Brown <broonie@kernel.org>