ANDROID: GKI: WWAN remove stale protected exports

aosp/2654422 introduced these stale symbols which are not
exported due to CONFIG_WWAN_DEBUGFS is disabled; and update
was generted with it enabled.

Stale symbols:
  - wwan_get_debugfs_dir
  - wwan_put_debugfs_dir

Fixes: 39cb6570 ("ANDROID: GKI: Add WWAN as GKI protected module")
Bug: 291528937
Test: bazel run //common:kernel_aarch64_abi_update
Change-Id: I469b6f0ac4645bda7aba52eaa24c3d02afd37c6b
Signed-off-by: Ramji Jiyani <ramjiyani@google.com>