Put inline asm directly into cortex-m-semihosting so it doesn't need to depend on cortex-m 0.8

Author: adamgreig

cortex-m-semihosting/src/lib.rs

@@ -194,7 +194,13 @@ pub unsafe fn syscall<T>(nr: usize, arg: &T) -> usize {
 pub unsafe fn syscall1(_nr: usize, _arg: usize) -> usize {
     match () {
         #[cfg(all(thumb, not(feature = "no-semihosting")))]
-        () => cortex_m::asm::semihosting_syscall(_nr as u32, _arg as u32) as usize,
+        () => {
+            use core::arch::asm;
+            let mut nr = _nr as u32;
+            let arg = _arg as u32;
+            asm!("bkpt #0xab", inout("r0") nr, in("r1") arg, options(nostack, preserves_flags));
+            nr as usize
+        },
         #[cfg(all(thumb, feature = "no-semihosting"))]
         () => 0,
         #[cfg(not(thumb))]