libpayload: serial: Move the depthcharge serial drivers into libpayload.

These drivers need to be ready right away and never really fit into the
depthcharge driver model anyway.

CQ-DEPEND=CL:194063
BUG=None
TEST=Built and booted on nyan and peach_pit. Built for nyan_big, nyan_blaze,
and daisy.
BRANCH=None

Original-Change-Id: I9570dee53c57d42ef4cd956f66a878ce39a2dc20
Original-Signed-off-by: Gabe Black <gabeblack@google.com>
Original-Reviewed-on: https://chromium-review.googlesource.com/194057
Original-Reviewed-by: Gabe Black <gabeblack@chromium.org>
Original-Commit-Queue: Gabe Black <gabeblack@chromium.org>
Original-Tested-by: Gabe Black <gabeblack@chromium.org>
(cherry picked from commit 26e18f680c93fc990a3d1057c164f19859634a9f)
Signed-off-by: Marc Jones <marc.jones@se-eng.com>

Change-Id: Ia2233e2bd821d8de8d2d57a9423aeb74be7efd93
Reviewed-on: http://review.coreboot.org/7224
Reviewed-by: Patrick Georgi <pgeorgi@google.com>
Tested-by: build bot (Jenkins)