msm: camera: Fix memory read security flaw

Adds bound check on reg_cfg_cmd->u.dmi_info.hi_tbl_offset.

IOCTL VIDIOC_MSM_VFE_REG_CFG uses usersupplied value without
performing bounds check for following cmd_type.
VFE_READ_DMI_16BIT
VFE_READ_DMI_32BIT
VFE_READ_DMI_64BIT

Change-Id: I554c45ef3a172f5b5891b67a7e8e7a1f3f3882ed
Signed-off-by: Trishansh Bhardwaj <tbhardwa@codeaurora.org>