WindCharger: Fix u-boot lower 16MB boundary checks

Originally boundary checks wouldn't see the end of the lower 16MB
partition, and would loop back over to the beginning of said partition
if a file was too large (ex: 17MB rootfs image).  This change fixes
that.

b/21668671

Change-Id: I482cf0787ea3c3fae4e8d31a7603976e8182a8e8
3 files changed