locking/atomic: m68k: add preprocessor symbols

Some atomics can be implemented in several different ways, e.g.
FULL/ACQUIRE/RELEASE ordered atomics can be implemented in terms of
RELAXED atomics, and ACQUIRE/RELEASE/RELAXED can be implemented in terms
of FULL ordered atomics. Other atomics are optional, and don't exist in
some configurations (e.g. not all architectures implement the 128-bit
cmpxchg ops).

Subsequent patches will require that architectures define a preprocessor
symbol for any atomic (or ordering variant) which is optional. This will
make the fallback ifdeffery more robust, and simplify future changes.

Add the required definitions to arch/m68k.

Signed-off-by: Mark Rutland <[e-mail]>
Signed-off-by: Peter Zijlstra (Intel) <[e-mail]>
Reviewed-by: Kees Cook <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]

arch/m68k/include/asm/atomic.h

···
 ATOMIC_OPS(add, +=, add)
 ATOMIC_OPS(sub, -=, sub)
 
+#define arch_atomic_add_return			arch_atomic_add_return
+#define arch_atomic_sub_return			arch_atomic_sub_return
+#define arch_atomic_fetch_add			arch_atomic_fetch_add
+#define arch_atomic_fetch_sub			arch_atomic_fetch_sub
+
 #undef ATOMIC_OPS
 #define ATOMIC_OPS(op, c_op, asm_op)					\
 	ATOMIC_OP(op, c_op, asm_op)					\
···
 ATOMIC_OPS(and, &=, and)
 ATOMIC_OPS(or, |=, or)
 ATOMIC_OPS(xor, ^=, eor)
+
+#define arch_atomic_fetch_and			arch_atomic_fetch_and
+#define arch_atomic_fetch_or			arch_atomic_fetch_or
+#define arch_atomic_fetch_xor			arch_atomic_fetch_xor
 
 #undef ATOMIC_OPS
 #undef ATOMIC_FETCH_OP