Revert "ANDROID: vendor_hooks: Add hooks to extend the struct swap_info_struct"

This reverts commit 667f0d71.

The hooks android_vh_init_swap_info_struct and android_vh_alloc_si are
not used by any vendor, so remove it to help with merge issues with
future LTS releases.

If this is needed by any real user, it can easily be reverted to add it
back and then the symbol should be added to the abi list at the same
time to prevent it from being removed again later.

Bug: 203756332
Bug: 234214858
Cc: Bing Han <bing.han@transsion.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>
Change-Id: If01c284ebf15e804e7cf34e854b7db0d5b68ae1b