U-Boot's Makefile passes KEYDIR to direct mkimage invocations, but
internal binman FIT builds only receive the generic BINMAN_INDIRS search
path. Adding KEYDIR to BINMAN_INDIRS treats it as one more input-file
search path: FIT entries still auto-detect a key directory from all
include directories, so an explicit KEYDIR may not be the directory that
gets passed to mkimage. It also makes a key-only directory part of the
generic blob lookup path.
Forward KEYDIR as a binman entry argument named keydir, matching the
existing entry-argument mechanism used for BL31, TEE, of-list and other
U-Boot build inputs. FIT entries use that directory directly for
mkimage -k when fit,sign or fit,encrypt is enabled, falling back to the
include-directory autodetection when keydir is not provided.
Signed-off-by: James Hilliard <james.hilliard1@gmail.com>