firmware: convert tg3 driver to request_firmware()

Firmware blob looks like this...
        u8 firmware_major
        u8 firmware_minor
        u8 firmware_fix
        u8 pad
        __be32 start_address
        __be32 length (total, including BSS sections to be zeroed)
        data... (in __be32 words, which is native for the firmware)

Signed-off-by: Jaswinder Singh Rajput <jaswinderrajput@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>