efi_loader: typedef struct efi_object *efi_handle_t

All our handles point to a struct efi_object. So let's define the
efi_handle_t accordingly. This helps us to discover coding errors much
more easily. This becomes evident by the corrections to the usage of
handles in this patch.

Rename variable image_handle to image_obj where applicable.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Signed-off-by: Alexander Graf <agraf@suse.de>
diff --git a/lib/efi_selftest/efi_selftest_devicepath.c b/lib/efi_selftest/efi_selftest_devicepath.c
index adcf531..105ce2c 100644
--- a/lib/efi_selftest/efi_selftest_devicepath.c
+++ b/lib/efi_selftest/efi_selftest_devicepath.c
@@ -257,7 +257,7 @@
 static int execute(void)
 {
 	struct efi_device_path *remaining_dp;
-	void *handle;
+	efi_handle_t handle;
 	/*
 	 * This device path node ends with the letter 't' of 'u-boot'.
 	 * The following '.bin' does not belong to the node but is