target/mips/cpu: Calculate the CP0 timer period using the CPU frequency

The CP0 timer period is a function of the CPU frequency.
Start using the default values, which will be replaced by
properties in the next commits.

Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
Message-Id: <20201012095804.3335117-10-f4bug@amsat.org>
1 file changed