arm64: entry.S: Add ventry overflow sanity checks

commit 4330e2c5c04c27bebf89d34e0bc14e6943413067 upstream.

Subsequent patches add even more code to the ventry slots.
Ensure kernels  that overflow ventry slot do not get built.

Change-Id: I93c5b565257efdddb704b2b477b6521c3440a334
Reviewed-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Git-commit: e8bfe29a
Git-repo: https://android.googlesource.com/kernel/common/


Signed-off-by: Kishor Krishna Bhat <quic_kishkris@quicinc.com>