powerpc: Fix misspellings in tlbflush.h

The comment marking the end of the include guard is wrong, fix it up.

Signed-off-by: Zhang Yunkai <zhang.yunkai@zte.com.cn>
[mpe: Rewrite commit message]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20210304031318.188447-1-zhang.yunkai@zte.com.cn

arch/powerpc/include/asm/book3s/32/tlbflush.h

@@ -79,4 +79,4 @@ static inline void local_flush_tlb_mm(struct mm_struct *mm)
 	flush_tlb_mm(mm);
 }
 
-#endif /* _ASM_POWERPC_TLBFLUSH_H */
+#endif /* _ASM_POWERPC_BOOK3S_32_TLBFLUSH_H */