video: ipu reg: Correct reserved1 array size in struct ipu_cm

The array reserved1 as a placeholder in the structure ipu_cm
should contain 4 32bit unsigned integer entries instead of 16
ones, because the placeholder is located bewteen the register
IPU_CH_DB_MODE_SEL_1 and the register IPU_ALT_CH_DB_MODE_SEL_0
with the address offsets of 0x154 and 0x168 respectively.

Reported-by: Robin Gong <b38343@freescale.com>
Acked-by: Robin Gong <b38343@freescale.com>
Cc: Stefano Babic <sbabic@denx.de>
Signed-off-by: Liu Ying <Ying.Liu@freescale.com>