KVM: arm64: Remove target_table from exit handlers

Whenever KVM searches for a register (e.g. due to a guest exit), it
works with two tables, as the target table overrides the sys_regs array.

Now that everything is in the sys_regs array, and the target table is
empty, stop doing that.

Remove the second table and its size from all the functions that take
it.

Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20200622113317.20477-5-james.morse@arm.com