cxgb4: Move firmware version MACRO to t4fw_version.h

Move firmware version MACRO to a new t4fw_version.h file so that csiostor driver
can also use it.

Signed-off-by: Hariprasad Shenai <hariprasad@chelsio.com>
Signed-off-by: David S. Miller <davem@davemloft.net>