drm/amd/amdgpu/amdgpu_psp: Make local function 'parse_ta_bin_descriptor' static

Fixes the following W=1 kernel build warning(s):

 drivers/gpu/drm/amd/amdgpu/amdgpu_psp.c:2576:5: warning: no previous prototype for ‘parse_ta_bin_descriptor’ [-Wmissing-prototypes]

Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: "Christian König" <christian.koenig@amd.com>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: amd-gfx@lists.freedesktop.org
Cc: dri-devel@lists.freedesktop.org
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdgpu/amdgpu_psp.c

@@ -2574,9 +2574,9 @@ out:
 	return err;
 }
 
-int parse_ta_bin_descriptor(struct psp_context *psp,
-			    const struct ta_fw_bin_desc *desc,
-			    const struct ta_firmware_header_v2_0 *ta_hdr)
+static int parse_ta_bin_descriptor(struct psp_context *psp,
+				   const struct ta_fw_bin_desc *desc,
+				   const struct ta_firmware_header_v2_0 *ta_hdr)
 {
 	uint8_t *ucode_start_addr  = NULL;