(split) Allow a hardware driver to pass clock frequencies into the sdhci driver.

The sdhci spec says that if the base or timeout clock frequency in the
capabilities register is zero, the driver must obtain the frequency "from
another source."  This change defines that other source to be the low-level
hardware driver, which can pre-set the frequencies in slot.max_clk and
slot.timeout_clk before calling sdhci_init_slot().

This helps with a growing number of SoCs that have sdhci base clock
frequencies that either won't fit into the range allowed by the number of
bits available in the capabilities register, or the frequency is runtime-
configurable.
(split) Add m_clrprotoflags() to clear protocol specific mbuf flags at up and
downwards layer crossings.

Consistently use it within IP, IPv6 and ethernet protocols.

Discussed with:	trociny, glebius
(split) Migrate the net80211 protocol specific use of M_FRAG, M_FIRSTFRAG and
M_LASTFRAG flags to protocol specific flags.

Remove the now unused M_FRAG, M_FIRSTFRAG and M_LASTFRAG mbuf flags.

Discussed with:	trociny, glebius, adrian
(split) Reorder the mbuf defines to make more sense and group related flags
together.

Add M_FLAG_PRINTF for use with printf(9) %b indentifier.

Use the generic mbuf flags print names in the net80211 code and adjust
the protocol specific bits for their new positions.

Change SCTP M_PROTO mapping from 5 to 1 to fit within the 16bit field
they use internally to store some additional information.

Discussed with:	trociny, glebius
(split) Add in some backwards compatability hacks to make -HEAD net80211 compile
on -9.
(split) Merge branch '7b6ce3e'