efi_loader: update the error message of TCG protocol installation

"Unable to find TPMv2 device" doesn't explain much with regards to the
error origin. Update it to match what we have in the RNG protocol
installation.

Signed-off-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
Reviewed-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
diff --git a/lib/efi_loader/efi_tcg2.c b/lib/efi_loader/efi_tcg2.c
index a525ebf..918e9a2 100644
--- a/lib/efi_loader/efi_tcg2.c
+++ b/lib/efi_loader/efi_tcg2.c
@@ -2417,7 +2417,7 @@
 
 	ret = platform_get_tpm2_device(&dev);
 	if (ret != EFI_SUCCESS) {
-		log_warning("Unable to find TPMv2 device\n");
+		log_warning("Missing TPMv2 device for EFI_TCG_PROTOCOL\n");
 		return EFI_SUCCESS;
 	}