Revert "bcm27xx-gpu-fw: update to latest version"

Revert "bcm27xx-gpu-fw: update to latest version"

This reverts commit 9e467a764b4e30a04dd0431ea277f6acd26babe0.

The Raspberry Pi firmware recently switched to building from the common
firmware branch. This introduces changes in the core clock handling,
causing various issues.

E.g. enable_uart=1 no longer fixes the core clock frequency to 250MHz.
When the disable-bt DT overlay is not loaded, the core clock frequency
is increased to 400MHz. As a result, the UART baud rate is no longer
correct, and this causes garbled serial console, or communication
problems with HATs that use the UART.

As a workaround, the core clock could be fixed to 250MHz by adding
'core_freq=250' in /boot/config.txt, but as there appear to be other
issues than just the UART being broken, the safer bet is to revert the
firmware for now.

Upstream bug: https://github.com/raspberrypi/firmware/issues/1376

Signed-off-by: Stijn Tintel <stijn@linux-ipv6.be>
Acked-by: Álvaro Fernández Rojas <noltari@gmail.com>