imx: mx6: fix reg base address when runtime usage

Should use parenthese to wrap the macro definition, otherwise
we will encounter error like the following:

"
if (base_addr != LCDIF1_BASE_ADDR) {
    puts("Wrong LCD interface!\n");
    return -EINVAL;
}
"

Without this patch, we will always encounter "Wrong LCD interface".

Signed-off-by: Peng Fan <Peng.Fan@freescale.com>
Cc: Stefano Babic <sbabic@denx.de>
Reviewed-by: Stefano Babic <sbabic@denx.de>