[media] s5p-jpeg: remove stray call to readl

There is no need to read INT_EN_REG before enabling interrupts.

Signed-off-by: Jacek Anaszewski <j.anaszewski@samsung.com>
Signed-off-by: Kamil Debski <k.debski@samsung.com>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>