Update to v5.6 kernel headers.

Kernel headers coming from:

Git: https://android.googlesource.com/kernel/common/
Branch: android-mainline
Tag: android-mainline-5.6

Add a new method for removing structures. This is to deal with the kernel
headers changing some definitions of timeval to __kernel_old_timeval
and itimerval to __kernel_old_itimerval. Remove the __kernel_old_XX
strutures and change the other structures to the previous definitions.

This only works so long as these structures stay the same, if they
diverge, then a different strategy will need to be implemented.

Test: Booted cuttlefish/walleye.
Test: Ran bionic-unit-tests on cuttlefish/walleye.
Change-Id: I0a61f4fa6e4155c602e0414d9b38c2e1637829af
diff --git a/libc/kernel/tools/clean_header.py b/libc/kernel/tools/clean_header.py
index 92a2139..2c2d001 100755
--- a/libc/kernel/tools/clean_header.py
+++ b/libc/kernel/tools/clean_header.py
@@ -112,6 +112,7 @@
     if arch and arch in kernel_arch_token_replacements:
         blocks.replaceTokens(kernel_arch_token_replacements[arch])
 
+    blocks.removeStructs(kernel_structs_to_remove)
     blocks.optimizeMacros(macros)
     blocks.optimizeIf01()
     blocks.removeVarsAndFuncs(kernel_known_generic_statics)