exec.h: fix coding style and change cpu_has_work to return bool

+ Remove obsolete env_to_regs + regs_to_env functions.

Upstream f3e270377acd074f62e08960ef9444adf67d3590

Change-Id: Idd7561fce7b9a92f2194d2a9a1b710d32dc61183
diff --git a/cpu-exec.c b/cpu-exec.c
index ee2ea87..17bc910 100644
--- a/cpu-exec.c
+++ b/cpu-exec.c
@@ -45,7 +45,7 @@
 //#define CONFIG_DEBUG_EXEC
 //#define DEBUG_SIGNAL
 
-int qemu_cpu_has_work(CPUOldState *env)
+bool qemu_cpu_has_work(CPUOldState *env)
 {
     return cpu_has_work(env);
 }