radeon: add firmware for Mullins/Beema GPUs

Add new ucode for Mullins/Beema GPUs and update
WHENCE entry.

Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

WHENCE

@@ -1588,6 +1588,12 @@ File: radeon/HAWAII_pfp.bin
 File: radeon/HAWAII_rlc.bin
 File: radeon/HAWAII_sdma.bin
 File: radeon/HAWAII_smc.bin
+File: radeon/MULLINS_ce.bin
+File: radeon/MULLINS_me.bin
+File: radeon/MULLINS_mec.bin
+File: radeon/MULLINS_pfp.bin
+File: radeon/MULLINS_rlc.bin
+File: radeon/MULLINS_sdma.bin
 
 Licence: Redistributable. See LICENSE.radeon for details.