Update kernel to 5.5.2

Between 5.4 and 5.5, apparently in commit 0e4a459f56c32d3e ("tracing:
Remove unnecessary DEBUG_FS dependency"), CONFIG_DEBUG_FS is no longer
auto-enabled. We're using that interface for obtaining an old-school
GPIO number because, well, that's what the LED GPIO trigger expects.

It would be nice to fix this upstream so that the LED GPIO trigger
accepts, say, a (chipname, gpio number) pair, but ENOTIME.

Change-Id: Ie4e3b37729389f03d7a294d0bc3cecc589ae5ed0
diff --git a/board/czechlight/beaglebone/linux.fragment b/board/czechlight/beaglebone/linux.fragment
index d4b75f3..d797963 100644
--- a/board/czechlight/beaglebone/linux.fragment
+++ b/board/czechlight/beaglebone/linux.fragment
@@ -2,3 +2,5 @@
 
 # calibration device
 CONFIG_PINCTRL_MCP23S08=y
+
+CONFIG_LOCALVERSION="-cla-bbb"