binder: fix binder_alloc kernel-doc warnings

Update the kernel-doc section of struct binder_alloc to fix the
following warnings reported by ./scripts/kernel-doc:

  warning: Function parameter or member 'mutex' not described in 'binder_alloc'
  warning: Function parameter or member 'vma_addr' not described in 'binder_alloc'

No functional changes in this patch.
Reviewed-by: Christian Brauner (Microsoft) <brauner@kernel.org>
Acked-by: Todd Kjos <tkjos@google.com>
Signed-off-by: Carlos Llamas <cmllamas@google.com>
Link: https://lore.kernel.org/r/20220906135948.3048225-4-cmllamas@google.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/android/binder_alloc.h

@@ -74,10 +74,9 @@ struct binder_lru_page {
 
 /**
  * struct binder_alloc - per-binder proc state for binder allocator
- * @vma:                vm_area_struct passed to mmap_handler
+ * @mutex:              protects binder_alloc fields
+ * @vma_addr:           vm_area_struct->vm_start passed to mmap_handler
  *                      (invariant after mmap)
- * @tsk:                tid for task that called init for this proc
- *                      (invariant after init)
  * @mm:                 copy of task->mm (invariant after open)
  * @buffer:             base of per-proc address space mapped via mmap
  * @buffers:            list of all buffers for this proc