Reset req_l latch on system reset

Even if the holding register of SRLatch is really reset-less, it is still
reset at startup, because the latch reset port has reset=1. But, this only
works if the latch reset port is driven by the sync domain. In case of
req_l, it's driven by the comb domain, so the latch is not reset on system
reset.

Generate a pulse on system reset, and combine it with the latch reset.