bnx2: drop unsupported firmwares

bnx2: drop unsupported firmwares

The stable kernels from 4.9 to current only support a number of
sub versions of the 7.13.x.y firmware versions, in the unlikely
scenario of a user needing an older rev they can be easily
ontained via old releases. The 4.x stable kernels depend on the
7.13.1 (as does the el7 kernel), 5.4 depends on 7.13.11, and
the 5.10 and later kernels all depend on 7.13.15/7.13.21. Let's
cleanup the quite sizable unused versions.

Signed-off-by: Peter Robinson <pbrobinson@gmail.com>
Signed-off-by: Josh Boyer <jwboyer@kernel.org>