ANDROID: GKI: defconfig: enable BTF debug info

Build BTF type info into the kernel to enable use of BPF-based tools
such as BCC's libbpf-tools.
By default, modules whose split BTF is inconsistent with vmlinux BTF
will fail to load, which can prevent loading compatible but separately
built modules. Instead, enable MODULE_ALLOW_BTF_MISMATCH to ignore
such modules' BTF rather than refusing to load the module.

Bug: 203823368
Bug: 218515241
Test: build
Signed-off-by: Connor O'Brien <connoro@google.com>
Change-Id: I8efaab5f1a5c6ad6e9e6ccf1e78088d81a880480