xen/arm: mark __guest_cmpxchg always_inline

When building the hypervisor with -Og, we run into a __bad_cmpxchg link error:

aarch64-none-linux-gnu-ld: prelink.o: in function `__int_cmpxchg':
.../xen/./arch/arm/include/asm/arm64/cmpxchg.h:117: undefined reference to `__bad_cmpxchg'
aarch64-none-linux-gnu-ld: .../xen/./arch/arm/include/asm/arm64/cmpxchg.h:117: undefined reference to `__bad_cmpxchg'
aarch64-none-linux-gnu-ld: ./.xen-syms.0: hidden symbol `__bad_cmpxchg' isn't defined
aarch64-none-linux-gnu-ld: final link failed: bad value

This is due to the function __guest_cmpxchg not being inlined in the -Og build
with gcc 12. Fix this by marking __guest_cmpxchg always_inline.

Signed-off-by: Stewart Hildebrand <stewart.hildebrand@amd.com>
Reviewed-by: Julien Grall <jgrall@amazon.com>
Reviewed-by: Henry Wang <Henry.Wang@arm.com>

xen/arch/arm/include/asm/guest_atomics.h

@@ -86,11 +86,11 @@ static inline void guest_clear_mask16(struct domain *d, uint16_t mask,
     domain_unpause(d);
 }
 
-static inline unsigned long __guest_cmpxchg(struct domain *d,
-                                            volatile void *ptr,
-                                            unsigned long old,
-                                            unsigned long new,
-                                            unsigned int size)
+static always_inline unsigned long __guest_cmpxchg(struct domain *d,
+                                                   volatile void *ptr,
+                                                   unsigned long old,
+                                                   unsigned long new,
+                                                   unsigned int size)
 {
     unsigned long oldval = old;