net/cadence/macb: fix bug/typo in extracting gem_irq_read_clear bit

[ Upstream commit 01276ed2424eb78c95461545410923d5da154d31 ]

Signed-off-by: Jongsung Kim <neidhard.kim@lge.com>
Acked-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>