alpha: locks: remove unused arch_*_relax operations

The arch_{spin,read,write}_relax macros are not used anywhere in the
kernel and are typically just aliases for cpu_relax().

This patch removes the unused definitions for Alpha.

Cc: Al Viro <[e-mail]>
Reviewed-by: Matt Turner <[e-mail]>
Signed-off-by: Matt Turner <[e-mail]>
Signed-off-by: Will Deacon <[e-mail]>

arch/alpha/include/asm/spinlock.h

···
 #define arch_read_lock_flags(lock, flags) arch_read_lock(lock)
 #define arch_write_lock_flags(lock, flags) arch_write_lock(lock)
 
-#define arch_spin_relax(lock)	cpu_relax()
-#define arch_read_relax(lock)	cpu_relax()
-#define arch_write_relax(lock)	cpu_relax()
-
 #endif /* _ALPHA_SPINLOCK_H */