hw/timer: Add ASPEED timer device model

hw/timer: Add ASPEED timer device model

Implement basic ASPEED timer functionality for the AST2400 SoC[1]: Up to
8 timers can independently be configured, enabled, reset and disabled.
Some hardware features are not implemented, namely clock value matching
and pulse generation, but the implementation is enough to boot the Linux
kernel configured with aspeed_defconfig.

[1] http://www.aspeedtech.com/products.php?fPath=20&rId=376

Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
Message-id: 1458096317-25223-2-git-send-email-andrew@aj.id.au
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>