psp_verstage: report developer mode to PSP

Add platform_report_mode function which report current developer mode
status to the PSP. L1 widevine app in the PSP will use this information
to select key box.

BUG=b:211058864
TEST=build and boot guybrush
TEST=build picasso chrome os boards

Signed-off-by: Kangheui Won <khwon@chromium.org>
Change-Id: I04b5fcfa338b485b36f1b946203f32823385c0b1
Reviewed-on: https://review.coreboot.org/c/coreboot/+/61369
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Jason Glenesk <jason.glenesk@gmail.com>
Reviewed-by: Raul Rangel <rrangel@chromium.org>
Reviewed-by: Karthik Ramasubramanian <kramasub@google.com>

src/soc/amd/picasso/psp_verstage/chipset.c

@@ -38,3 +38,9 @@ int platform_set_sha_op(enum vb2_hash_algorithm hash_alg,
 	}
 	return 0;
 }
+
+void platform_report_mode(int developer_mode_enabled)
+{
+	/* Picasso PSP doesn't support this */
+	(void)developer_mode_enabled;
+}