efi_loader: capitalize EFI_LOCATE_SEARCH_TYPE values

Constants should be capitalized.
So rename the values of enum efi_locate_search_type.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Reviewed-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Alexander Graf <agraf@suse.de>