rt2x00: Split rt2x00dev->flags

The number of flags defined for the rt2x00dev->flags field,
has been growing over the years. Currently we are approaching
the maximum number of bits which are available in the field.

A secondary problem, is that one part of the field are initialized only
during boot, because the driver requirements are initialized or device
requirements are loaded from the EEPROM. In both cases, the flags are
fixed and will not change during device operation. The other flags are
the device state, and will change frequently. So far this resulted in the fact
that for some flags, the atomic bit accessors are used, while for the others
the non-atomic variants are used.

By splitting the flags up into a "flags" and "cap_flags" we can put all flags
which are fixed inside "cap_flags". This field can then be read non-atomically.
In the "flags" field we keep the device state, which is going to be read atomically.

This adds more room for more flags in the future, and sanitizes the field access methods.

Signed-off-by: Ivo van Doorn <IvDoorn@gmail.com>
Acked-by: Helmut Schaa <helmut.schaa@googlemail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>