lantiq: kernel 4.14: Remove reboot/remove reset asserts

Backport patch accepted upstream which removes the reset asserts of the
xrx200 gphy driver on reboot/remove.

While doing a global software reset, these bits are not cleared and let
some bootloader fail to initialise the GPHYs. The bootloader don't expect
these bits to be set, as they aren't during power on.

The asserts were a workaround for a wrong syscon-reboot mask. With a mask
set which includes the GPHY resets of the first reset register, the
resets of the second reset register arn't required any more.

Signed-off-by: Mathias Kresin <dev@kresin.me>