hw/misc: avr: Add limited support for power reduction device

hw/misc: avr: Add limited support for power reduction device

This is a simple device of just one register, and whenever this
register is written to it calls qemu_set_irq function for each
of 8 bits/IRQs. It is used to implement AVR Power Reduction.

[AM: Remove word 'Atmel' from filenames and all elements of code]
Suggested-by: Aleksandar Markovic <aleksandar.m.mail@gmail.com>
Signed-off-by: Michael Rolnik <mrolnik@gmail.com>
Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
[rth: Squash include fix and file rename from f4bug]
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Aleksandar Markovic <aleksandar.m.mail@gmail.com>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Thomas Huth <huth@tuxfamily.org>
Message-Id: <20200705140315.260514-22-huth@tuxfamily.org>