efivarfs: remove unused efi_variable.Attributes and efivar_entry.kobj

These fields look to be remnants of older code: Attributes was likely
meant to stash the variable attributes, but doesn't because we always
read them from the variable store and kobj was likely left over from
an older iteration of code where we manually created the objects
instead of using a filesystem.

[ ardb: these fields were used by the sysfs based 'efivars' precursor to
	efivarfs, which was removed in commit 0f5b2c69 ("efi: vars:
	Remove deprecated 'efivars' sysfs interface") ]

Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>