[SCSI] atari_NCR5380, sun3_NCR5380: operator precedence fix

SR_REQ is defined 0x20, but bitanding has no effect because '!' has a higher
priority than '&'

Signed-off-by: Roel Kluin <12o3l@tiscali.nl>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>