target-arm: Add QOM subclasses for each ARM cpu implementation

target-arm: Add QOM subclasses for each ARM cpu implementation

Register subclasses for each ARM CPU implementation.

Let arm_cpu_list() enumerate CPU subclasses in alphabetical order,
except for special value "any".

Replace cpu_arm_find_by_name()'s string -> CPUID lookup by storing the
CPUID (aka MIDR, Main ID Register) value in the class.

Signed-off-by: Andreas Färber <afaerber@suse.de>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>