docs(zynqmp): update the make command

Update the make command with the RESET_TO_BL31=1 addition.

Signed-off-by: Venkatesh Yadav Abbarapu <venkatesh.abbarapu@xilinx.com>
Change-Id: I46cc81abb539773706348464b3061d20d94522e9
1 file changed