gpio-langwell is a deprecated name. Despite the driver was made
initially for Langwell, it supports now other Intel Mid SoC's.

This patch does no change beside the file renaming with Kconfig/Makefile
update.
Signed-off-by: NDavid Cohen <david.a.cohen@linux.intel.com>
Signed-off-by: NLinus Walleij <linus.walleij@linaro.org>