exec: Rename cpu.c -> cpu-target.c

We have exec/cpu code split in 2 files for target agnostic
("common") and specific. Rename 'cpu.c' which is target
specific using the '-target' suffix. Update MAINTAINERS.
Remove the 's from 'cpus-common.c' to match the API cpu_foo()
functions.

Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Anton Johansson <anjo@rev.ng>
Message-Id: <20230914185718.76241-7-philmd@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
diff --git a/meson.build b/meson.build
index 21a1bc0..0760c29 100644
--- a/meson.build
+++ b/meson.build
@@ -3431,8 +3431,8 @@
   system_ss.add(when: 'CONFIG_WIN32', if_true: [files('os-win32.c')])
 endif
 
-common_ss.add(files('cpus-common.c'))
-specific_ss.add(files('cpu.c'))
+common_ss.add(files('cpu-common.c'))
+specific_ss.add(files('cpu-target.c'))
 
 subdir('softmmu')