soc: fsl: guts: remove module_exit() and fsl_guts_remove()

This driver will never be unloaded. Firstly, it is not available as a
module, but more importantly, other drivers will depend on this one to
apply possible chip errata.

Signed-off-by: Michael Walle <michael@walle.cc>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>