CRIS: Remove last traces of legacy RTC drivers

These legacy drivers were removed in commit
9c75fc8c ("CRIS: Remove legacy RTC
drivers"). Now remove their last traces in two Kconfig files and one
Makefile.

Signed-off-by: Paul Bolle <pebolle@tiscali.nl>
Signed-off-by: Jesper Nilsson <jespern@axis.com>