boot: downgrade EFI_MEMORY_ATTRIBUTE_PROTOCOL warning

U-Boot currently does not implement EFI_MEMORY_ATTRIBUTE_PROTOCOL
even when reporting EFI version >= 2.10. Consequently, systemd-boot
emits a warning on every boot when running on U-Boot firmware.

The absence of EFI_MEMORY_ATTRIBUTE_PROTOCOL is a current
U-Boot limitation and not a condition users can remedy.
Furthermore, the EFI specification does not require all
firmware advertising EFI 2.10 or newer to implement the
protocol. As a result, the warning provides little value on
U-Boot systems while causing log_wait() to impose a 2.5-second
boot delay.

Downgrade the message to LOG_DEBUG, this keeps the diagnostic
available for debugging purposes without penalizing normal
boot time.

Signed-off-by: Aswin Murugan <aswin.murugan@oss.qualcomm.com>

src/boot/linux.c

@@ -267,10 +267,7 @@ EFI_STATUS linux_exec(
                  * if required for NX_COMPAT */
                 err = BS->LocateProtocol(MAKE_GUID_PTR(EFI_MEMORY_ATTRIBUTE_PROTOCOL), /* Registration= */ NULL, (void **) &memory_proto);
                 if (err != EFI_SUCCESS)
-                        /* Only warn if the UEFI should have support in the first place (version >= 2.10) */
-                        log_full(err,
-                                 ST->Hdr.Revision >= ((2U << 16) | 100U) ? LOG_WARNING : LOG_DEBUG,
-                                 "No EFI_MEMORY_ATTRIBUTE_PROTOCOL found, skipping NX_COMPAT support.");
+                        log_debug_status(err, "No EFI_MEMORY_ATTRIBUTE_PROTOCOL found, skipping NX_COMPAT support.");
         }
 
         const PeSectionHeader *headers;