mtd: inftl: misplaced parenthesis in find_boot_record

The parenthesis was misplaced, upon error a one was shown.

[dwmw2: Fix the code not to do the assignment within the if() statement]
Signed-off-by: Roel Kluin <roel.kluin@gmail.com>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>