[CORE] Move rtc, input, and fb frameworks to drivers

The prime purpose of keeping rtc, input, and fb device frameworks
in core code was a potential future change which will make these
framework implementation very virtualization (and/or Xvisor) centric.

Currently, we use vmm_wallclock to emulate rtc devices. In future,
we will have per-guest input event listeners and per-guest display
for keyboard, mouse, and frame-buffer emulation. This facts provide
enough motivation to move rtc, input, and fb device frameworks to
drivers.

Signed-off-by: Anup Patel <anup@brainfault.org>