efi_loader: memory leak in append value

When printing an UEFI variable an error may arise while converting an
illegal hexadecimal value. In this case a buffer is leaked.

Close the memory leak. Provide an error message.

Reported-by: Coverity (CID 185830)
Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
1 file changed