ia64: fix EFI_DEBUG build

When enabled local debugging via `#define EFI_DEBUG 1` noticed build
failure:

    arch/ia64/kernel/efi.c:564:8: error: 'i' undeclared (first use in this function)

While at it fixed benign string format mismatches visible only when
EFI_DEBUG is enabled:

    arch/ia64/kernel/efi.c:589:11:
        warning: format '%lx' expects argument of type 'long unsigned int',
        but argument 5 has type 'u64' {aka 'long long unsigned int'} [-Wformat=]

Link: https://lkml.kernel.org/r/20210328212246.685601-1-slyfox@gentoo.org
Fixes: 14fb4209

 ("efi: Merge EFI system table revision and vendor checks")
Signed-off-by: Sergei Trofimovich <slyfox@gentoo.org>
Cc: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>