While the EFI spec allows numbers to be in many forms, libefivar
produces hex numbers for the dsn. Since that come is from EDK2, change
this for symmetry, by generating the dsn as a hex number.

Noticed by: gpart list | grep efimedia | awk -F: '{print $2;}' | \
sed -e 's/^ *//g;s/,,/,/' | grep MBR | efidp -p | efidp -f
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