semihosting: Split out semihost_sys_write

Split out the non-ARM specific portions of SYS_WRITE to a
reusable function.  This handles all GuestFD.  This removes
the last use of common_semi_syscall_len.

Note that gdb_do_syscall %x reads target_ulong, not int.

Reviewed-by: Luc Michel <lmichel@kalray.eu>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
diff --git a/include/semihosting/syscalls.h b/include/semihosting/syscalls.h
index 20da813..2464467 100644
--- a/include/semihosting/syscalls.h
+++ b/include/semihosting/syscalls.h
@@ -33,4 +33,10 @@
 void semihost_sys_read_gf(CPUState *cs, gdb_syscall_complete_cb complete,
                           GuestFD *gf, target_ulong buf, target_ulong len);
 
+void semihost_sys_write(CPUState *cs, gdb_syscall_complete_cb complete,
+                        int fd, target_ulong buf, target_ulong len);
+
+void semihost_sys_write_gf(CPUState *cs, gdb_syscall_complete_cb complete,
+                           GuestFD *gf, target_ulong buf, target_ulong len);
+
 #endif /* SEMIHOSTING_SYSCALLS_H */