ath5k: fix endianness of bitwise ops when installing mic

Fix these bugs found by sparse:

    ath5k/pcu.c:1102:21: warning: restricted __le32 degrades to integer
    ath5k/pcu.c:1102:13: warning: incorrect type in assignment (different base types)
    ath5k/pcu.c:1102:13:    expected restricted __le32 <noident>
    ath5k/pcu.c:1102:13:    got unsigned int
    ath5k/pcu.c:1104:20: warning: restricted __le32 degrades to integer
    ath5k/pcu.c:1104:13: warning: incorrect type in assignment (different base types)
    ath5k/pcu.c:1104:13:    expected restricted __le32 <noident>
    ath5k/pcu.c:1104:13:    got unsigned int

Changes-licensed-under: ISC

Reported-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: Bob Copeland <me@bobcopeland.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>