Simply add Makefile and Kconfig entries.

[hverkuil@xs4all.nl: auto-select I2C_SI4713]
Signed-off-by: NEduardo Valentin <eduardo.valentin@nokia.com>
Signed-off-by: NHans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: NMauro Carvalho Chehab <mchehab@redhat.com>