package/rpi-firmware: bump revision

Fixes in firmware:
  - misc: SDRAM calibration
  - camera: burst performance, exposure, EXIF
  - audio: noise in multichannel output, 8-bit input, float input/output,
           non-power-of-2 multi-channel
  - video: SEI in h264 encoder

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

package/rpi-firmware/rpi-firmware.mk

@@ -4,7 +4,7 @@
 #
 ################################################################################
 
-RPI_FIRMWARE_VERSION = 089cfb05ec350505ee84a99d567474c5bdc0505e
+RPI_FIRMWARE_VERSION = 9c7c2cd698ae24022c7aa74b16436c2966e82624
 RPI_FIRMWARE_SITE = $(call github,raspberrypi,firmware,$(RPI_FIRMWARE_VERSION))
 RPI_FIRMWARE_LICENSE = BSD-3c
 RPI_FIRMWARE_LICENSE_FILES = boot/LICENCE.broadcom