amd64_edac: Fix condition to verify max channels allowed for F15 M30h

The value returned from 'f15_m30h_determine_channel' will
always be 0x3 max. The condition

	(channel > 4 || channel < 0)

works as hardware never returns a value of 4, but
it leads to static checker analysis errors like
http://marc.info/?l=linux-edac&m=138607615131951&w=2

.

Fix that.

Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Aravind Gopalakrishnan <Aravind.Gopalakrishnan@amd.com>
Link: http://lkml.kernel.org/r/20131203130857.GA32170@elgon.mountain


[ Boris: massage commit message a bit. ]
Signed-off-by: Borislav Petkov <bp@suse.de>