powerpc: Remove proc_trap()

proc_trap() has never been used, remove it.
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/827944ea12d470c2f862635f48b5ee6c1520351f.1623217909.git.christophe.leroy@csgroup.eu

arch/powerpc/include/asm/reg.h

@@ -1436,8 +1436,6 @@ static inline void mtsr(u32 val, u32 idx)
 }
 #endif
 
-#define proc_trap()	asm volatile("trap")
-
 extern unsigned long current_stack_frame(void);
 
 register unsigned long current_stack_pointer asm("r1");