xc7: Fix dependencies for different boards
xc7: Fix dependencies for different boards

Clear variable DEVICE_RR_PATCH_DEPS before
appending new dependencies to it.

Signed-off-by: Lukasz Dalek <695c38bff956529fae97aed0393d4847bb29b4f7@antmicro.com>

SymbiFlow/symbiflow-arch-defs,SymbiFlow/symbiflow-arch-defs