[SCSI] qla2xxx: fix regression on sparc64

Some sparc64 boxes don't have a valid NVRAM (from which the driver
takes its WWPN) try to extract this from open firmware instead and if
that fails, fall back to a default, which would be invalid if more
than one machine on the same SAN does this, since two machines with
the same WWPN would be illegal, so warn when taking this potentially
invalid default.

Tested on SunBlade-1000:

Acked-by: Andrew Vasquez <andrew.vasquez@qlogic.com>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>