[media] msp3400: use IS_ENABLED check instead of #if

[media] msp3400: use IS_ENABLED check instead of #if

A recent patch broke the msp3400 driver when CONFIG_MEDIA_CONTROLLER
is not set:

drivers/media/i2c/msp3400-driver.h:107:5: error: "CONFIG_MEDIA_CONTROLLER" is not defined [-Werror=undef]

It was clearly a typo, and this patch changes the
"#if CONFIG_MEDIA_CONTROLLER" to a working IS_ENABLED() check.

Fixes: 27c189eed1f7 ("[media] msp3400: initialize MC data")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>