add mtvec_addr_i port

Created by: silabs-PaulZ

MTVEC will reset to mtvec_addr_i during first cycle of boot up.

Also made the boot_addr_i and dm_halt_addr_i ports consistent by passing whole vector ([31:0]) into submodules.

Fixes issue #401 (closed)

Signed-off-by: Paul Zavalney paul.zavalney@silabs.com