ath9k: Fix bug when using a card with a busted EEPROM

ath9k: Fix bug when using a card with a busted EEPROM

backport of commit 85efc86eb7c6cbb1c8ce8d99b10b948be033fbb9 upstream.

We fail if your EEPROM is busted but we were never propagated the
error back so such users could end up with a cryptic oops message
like:

IP: [<f883e1b9>] ath9k_reg_apply_world_flags+0x29/0x130 [ath9k]
*pde = 00000000
Oops: 0000 [#1] SMP
Modules linked in: ath9k(+) mac80211 cfg80211
Pid: 4284, comm: insmod Not tainted (2.6.29-wl #3) 7660A14
EIP: 0060:[<f883e1b9>] EFLAGS: 00010286 CPU: 1
EIP is at ath9k_reg_apply_world_flags+0x29/0x130 [ath9k]

Fix this by propagating the error and also lets not leave the
user in the dark and communicate what's going on. When this
happens you will now see this:

ath9k 0000:16:00.0: PCI INT A -> GSI 16 (level, low) -> IRQ 16
ath9k: Invalid EEPROM contents

Signed-off-by: Luis R. Rodriguez <lrodriguez@atheros.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>