This patch reduces the console buffer size from 2048 to 1024, thus fixes
OCM overwriting issue.

Differences are in bss section as is shown from output:
xilinx_versal_mini: all -2056 bss -2048 text -8
   u-boot: add: 0/0, grow: 0/-3 bytes: 0/-2056 (-2056)
     function                                   old     new   delta
     cli_simple_run_command                     340     332      -8
     static.lastcommand                        2049    1025   -1024
     console_buffer                            2049    1025   -1024

Better would be to use PPU RAM but this change is also aligned with changes
done in ZynqMP mini configurations.

Signed-off-by: Ashok Reddy Soma <ashok.reddy.soma@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>