Revert "dtc: update patch to apply to 1.4, drop SRCREV override"

This reverts commit 8193b3b837f6b8895955171db4783448ffe246e9.
dtc: update to 1.4.0 and update dynamic-symbols-fixup-support-patch

latest mainline u-boot complains for dtc's minimum version 1.4.0

Signed-off-by: Andreas Müller <schnitzeltony@googlemail.com>