lib: move rtc-lib.c to lib

Function rtc_to_tm() is needed for FAT file system support even if we don't
have a real time clock. So move it from drivers/ to lib/.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
3 files changed