package/rpi-firmware: bump version

Fixes and improvements for USB, audio sync, camera support,
codecs, HDMI framerate and audio, and GPU freezes.

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>

package/rpi-firmware/rpi-firmware.mk

@@ -4,7 +4,7 @@
 #
 ################################################################################
 
-RPI_FIRMWARE_VERSION = 320084a
+RPI_FIRMWARE_VERSION = d4f5315
 RPI_FIRMWARE_SITE = http://github.com/raspberrypi/firmware/tarball/$(RPI_FIRMWARE_VERSION)
 RPI_FIRMWARE_LICENSE = BSD-3c
 RPI_FIRMWARE_LICENSE_FILES = boot/LICENCE.broadcom