tty: Change dependency of ARCH_EXYNOS4

This patch changes dependency of ARCH_EXYNOS4 from ARCH_S5PV310
according to the change of ARCH name, EXYNOS4.

Cc: Ben Dooks <ben-linux@fluff.org>
Cc: Greg Kroah-Hartman <gregkh@suse.de>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>