video: fbdev: kconfig: Add help text to FB_I810_I2C

The FB_I810_I2C symbol previously had a blank help text, which was
removed in e9829ac4 ("video: fbdev: kconfig: Remove blank help
text").

Give it a proper help text, derived from commit 74f6ae84 ("[PATCH]
i810fb: Add > i2c/DDC support").

Signed-off-by: Ulf Magnusson <ulfalizer@gmail.com>
Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: "Luis R . Rodriguez" <mcgrof@kernel.org>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Cc: Paul Bolle <pebolle@tiscali.nl>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Michal Simek <michal.simek@xilinx.com>
Cc: Hans de Goede <j.w.r.degoede@gmail.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>