sim: bfin: include devices.h to fix build warnings

sim: bfin: include devices.h to fix build warnings

The place where these funcs get defined do not include the header that
declares their prototypes.  Add that to fix -Wmissing-prototypes:

devices.c:59:1: warning: no previous prototype for 'dv_bfin_mmr_invalid'
devices.c:66:1: warning: no previous prototype for 'dv_bfin_mmr_require'
devices.c:99:1: warning: no previous prototype for 'dv_bfin_mmr_check'
devices.c:159:14: warning: no previous prototype for 'dv_get_bus_num'

Signed-off-by: Mike Frysinger <vapier@gentoo.org>