p54: fix misbehavings when firmware can't be found

This patch fixes a double-free error in p54pci
( http://bugzilla.kernel.org/show_bug.cgi?id=11782 )

Trying to free already-free IRQ 10
Pid: 108, comm: pccardd Not tainted 2.6.27-05577-g0cfd810-dirty #1
Call Trace:
 [<c01265dc>] free_irq+0xad/0xb9
 [<c01050dd>] dma_generic_alloc_coherent+0x0/0xd7
 [<c01ba8e6>] p54p_stop+0x4a/0x1fa
 [<c01050dd>] dma_generic_alloc_coherent+0x0/0xd7
 [<c02348c5>] p54p_probe+0x23e/0x302

Tested-by: Sean Young
Signed-off-by: Christian Lamparter <chunkeey@web.de>
Signed-off-by: John W. Linville <linville@tuxdriver.com>