The current synchronous execution function doesn't work
for certain Hermes commands which clear the MAGIC number from
SWSUPPORT0. These commands seem to be related to initialisation or
programming, for example HERMES_CMD_INIT.

Replicate hermes_docmd_wait for commands which clear the MAGIC number
from SWSUPPORT0. This version accepts two extra arguments which are
passed straight to the firmware.

Functionality copied out of hermes_init.
Signed-off-by: David Kilroy <kilroyd@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>