MFC r268971 and r269032.

r268971:
Simplify r267600, there's no need to distinguish between allocated and
inlined mbufs.

r269032:
cxgbe(4):  Keep track of the clusters that have to be freed by the
custom free routine (rxb_free) in the driver.  Fail MOD_UNLOAD with
EBUSY if any such cluster has been handed up to the kernel but hasn't
been freed yet.  This prevents a panic later when the cluster finally
needs to be freed but rxb_free is gone from the kernel.
MFC r269106:

Add a 'raw' parameter to the 'modinfo' subcommand.  This is handy when
trying to figure out why a QSFP+/SFP+ connector or cable wasn't
identified correctly by cxgbe(4).  Its output looks like this:

# cxgbetool t5nex0 modinfo 0 raw
00:  03 04 21 00  00 00 00 00  ..!. ....
08:  04 00 00 00  67 00 00 00  .... g...
10:  00 00 05 00  41 6d 70 68  .... Amph
18:  65 6e 6f 6c  20 20 20 20  enol
20:  20 20 20 20  00 41 50 48       .APH
28:  35 37 31 35  34 30 30 30  5715 4000
30:  33 20 20 20  20 20 20 20  3
38:  4b 20 20 20  01 00 00 fa  K    ....
40:  00 00 00 00  41 50 46 31  .... APF1
48:  30 30 34 30  30 33 30 30  0040 0300
50:  30 33 20 20  31 30 30 31  03   1001
58:  33 30 20 20  00 00 00 97  30   ....