configs: imxrt1050-evk: temporary disable DCACHE
mxsfb needs a dcache function not implemented in cortex-M7, so for the
moment let's keep dcache not enabled.
Signed-off-by: Giulio Benetti <giulio.benetti@benettiengineering.com>
Reviewed-by: Anatolij Gustschin <agust@denx.de>