net80211: provide rate validation for injected frames.
There may be various side effects (device timeout, firmware and / or
kernel panic) when an invalid (or inapplicable - e.g., an MCS rate
for 11g-only device) is set; check rates before sending the frame to
the driver.
How-to-reproduce:
Set an MCS (real or bogus - with 0x80 bit set) rate in ibp_rate0 field
for any device that uses ieee80211_isratevalid() for rate checks -
rum(4), run(4), ural(4), bwi(4) or ral(4); if kernel is compiled
with INVARIANTS the check will result in "rate %d is basic/mcs?" panic.
Tested with WUSB54GC (rum(4)), AP mode.
MFC after: 1 week
UnifiedSplitRaw
