sbat: Don't assume VirtualSize == SizeOfRawData
sbat: Don't assume VirtualSize == SizeOfRawData

The current code rejects the .sbat section if the VirtualSize and
SizeOfRawData fields of the section header aren't the same, but this
is too strict. The VirtualSize corresponds to the size of the SBAT
metadata and isn't necessarily a multiple of the file alignment.
The on-disk size (SizeOfRawData) is a multiple of the file alignment
and is zero padded. Make sure that the on-disk size is at least as
large as virtual size, and ignore the .sbat section if it isn't.

This should fix https://github.com/rhboot/shim/issues/281.

Signed-off-by: Chris Coulson <2226e81bcfd16343442e8c1ae73e4a3d230c336a@canonical.com>

rhinstaller/shim,rhinstaller/shim,rhinstaller/shim