baseboard-octopus: add a build flag for RTL8822C

This change updates LINUX_FIRMWARE (which expends into a USE flag)
in order to pick the correct Bluetooth firmware file on RTL8822C.

BUG=b:139078086
TEST=Manually run with and without the chages (and depedencies), and verify
that the FW was loaded correctly by checking the FW version in the log

Change-Id: I02ad2dad3fcadcdd9871c96a9d93dbb5e86a3f12
Reviewed-on: https://chromium-review.googlesource.com/1742929
Tested-by: Yoni Shavit <yshavit@chromium.org>
Commit-Ready: Yoni Shavit <yshavit@chromium.org>
Legacy-Commit-Queue: Commit Bot <commit-bot@chromium.org>
Reviewed-by: Justin TerAvest <teravest@chromium.org>
Reviewed-by: Brian Norris <briannorris@chromium.org>
(cherry picked from commit 66a840395cba13cc3290dcd135c2a0bf4b032246)
diff --git a/baseboard-octopus/profiles/base/make.defaults b/baseboard-octopus/profiles/base/make.defaults
index aaa14dc..a1eda98 100644
--- a/baseboard-octopus/profiles/base/make.defaults
+++ b/baseboard-octopus/profiles/base/make.defaults
@@ -20,6 +20,9 @@
 # RTL8822C WiFi firmware
 LINUX_FIRMWARE="${LINUX_FIRMWARE} rtw8822c"
 
+# RTL8822C BT firmware
+LINUX_FIRMWARE="${LINUX_FIRMWARE} rtl_bt-8822c"
+
 # Enable EC logging
 USE="${USE} eclog"