Revert "ANDROID: Make vsock virtio packet buff size configurable"

This reverts commit f465fb7e.

Now that vsock is more careful with its page allocations, overriding
this option doesn't achieve an awful lot.

Bug: 421244320
Bug: 149494272
Bug: 436528862
Signed-off-by: Will Deacon <willdeacon@google.com>
Change-Id: I3ff4e92407f97f547528da459c1dad3519eb8b04