x86: ivybridge: remove unused uma_memory_size

The value of uma_memory_size depends on an undefined value
from the stack. The value of uma_memory_size is changed but
never used.

So simply remove this superfluous code.

The problem was indicated by cppcheck.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>