[PATCH] zd1211rw: cleanups

Bit-field constants in zd_chip.h are now defined using a shift expression.
The value 0x08 is now (1 << 3). The fix is intended to improve readability.

Remove misleading comment in zd_mac.c: The function already returns -EPERM
in managed mode (IW_MODE_INFRA).

Remove unused code in zd_mac.c: The unused code intended for debugging
rx_status values is no longer useful.

Added dump_stack() to ZD_ASSERT macro: Output of the stack helps to debug
assertions. Keep in mind that the ZD_ASSERT() macro only results in code,
if DEBUG is defined.

Improved comments for filter_rx()

zd_usb.c: Added driver name to module init and exit functions

Signed-off-by: Ulrich Kunitz <kune@deine-taler.de>
Signed-off-by: Daniel Drake <dsd@gentoo.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>