x86/efi: remove unused variables

commit ad723674 ("x86/efi: move common keyring handler functions
to new file") leave this unused.

Fixes: ad723674 ("x86/efi: move common keyring handler functions to new file")
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Link: https://lore.kernel.org/r/20191115130830.13320-1-yuehaibing@huawei.com