ab5500-core.c: Don't needlessly include linux/version.h

As 'make versioncheck' so nicely points out, there's no need for
drivers/mfd/ab5500-core.c to #include the linux/version.h header.
This patch removes the pointless include.

Signed-off-by: Jesper Juhl <jj@chaosbits.net>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>