MIPS jazz is the last user of the legacy esp_init() function so move creation
of the ESP device over to use qdev.

Note that the esp_reset and dma_enable qemu_irqs are currently unused and so
we do not wire these up and instead remove the variables to prevent the
compiler emitting unused variable warnings.

Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
Message-Id: <20180613094727.11326-2-mark.cave-ayland@ilande.co.uk>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Tested-by: Hervé Poussineau <hpoussin@reactos.org>