arm: mx28: fix bit operation in clock setting

reg | (1 << clk->enable_shift) always evaluates to true. Switch it
to & which makes much more sense. Same fix as 13be9f00 (ARM i.MX28: fix
bit operation) at a different location.

Signed-off-by: Wolfram Sang <w.sang@pengutronix.de>
Cc: Sascha Hauer <s.hauer@pengutronix.de>
Cc: Shawn Guo <shawn.guo@freescale.com>
Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
Cc: stable@kernel.org
Signed-off-by: Arnd Bergmann <arnd@arndb.de>