efi: Add missing prototype for efi_capsule_setup_info

Fixes "no previous declaration for 'efi_capsule_setup_info'" warnings
under W=1.

Fixes: 2959c95d ("efi/capsule: Add support for Quark security header")
Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Link: https://lore.kernel.org/r/c28d3f86-dd72-27d1-e2c2-40971b8da6bd@siemens.com


Signed-off-by: Ard Biesheuvel <ardb@kernel.org>