[SCSI] bfa: Replace large udelay() with mdelay()

udelay() does not work on some architectures for values above
2000, in particular on ARM:

ERROR: "__bad_udelay" [drivers/scsi/bfa/bfa.ko] undefined!

Reported-by: Vagrant Cascadian <vagrant@debian.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>