cxgb4: Delete unused file cxgb4/t4fw-1.3.10.0.bin

There doesn't appear to be any driver version that will request the
file "cxgb4/t4fw-1.3.10.0.bin".  The current version requests
"cxgb4/t4fw.bin" which remains as a symlink.

Signed-off-by: Ben Hutchings <ben@decadent.org.uk>