i2c-bridge: Updated bridge and slave modules

Bridge: Removed "redundant" SIM_WB_TRANSFER state.

Slave: Removed redundant ADDR_CHECK state and moved its code to
the ADDR state.

Also corrected a bug whereby the ack_i pin was not being checked within
the ADDR_ACK state. This was causing the FSM to advance even thogh the
slave was actually NACK-ing.

DOC: Updated documentation for both these modules

Signed-off-by: Theodor Stana <t.stana@cern.ch>