fs: efivars: read the attributes on the second get_variable()
Some EFI get_variable() implementations don't set the attributes when
returning EFI_BUFFER_TOO_SMALL.
Signed-off-by: Michael Olbrich <m.olbrich@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>