common: cmd_bdinfo: Fix compilation warning for microblaze

Fix one printf compilation warning in microblaze bdinfo part.

Warning log:
cmd_bdinfo.c: In function 'do_bdinfo':
cmd_bdinfo.c:219:2: warning: format '%u' expects argument of type
'unsigned int', but argument 2 has type 'long unsigned int' [-Wformat]

Signed-off-by: Michal Simek <michal.simek@xilinx.com>