MPC8572DS: Fix compile warnings

Commit 445a7b38 introduced the following
compile warnings:

cmd_i2c.c:112: warning: missing braces around initializer
cmd_i2c.c:112: warning: (near initialization for 'i2c_no_probes[0]')

Signed-off-by: Kumar Gala <galak@kernel.crashing.org>