extcon: fsa9480: Fix Kconfig warning and build errors

Fix Kconfig dependency warning and subsequent build errors caused by
the Kconfig entry for EXTCON-FSA9480.  It should not select
REGMAP_I2C unless I2C is already set/enabled.

WARNING: unmet direct dependencies detected for REGMAP_I2C
  Depends on [n]: I2C [=n]
  Selected by [y]:
  - EXTCON_FSA9480 [=y] && EXTCON [=y] && INPUT [=y]

Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
[cw00.choi: adjust the patch title and remove the long warning messages]
Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>