csky: syscache: Fixup duplicate cache flush

The current csky logic of sys_cacheflush is wrong, it'll cause
icache flush call dcache flush again. Now fixup it with a
conditional "break & fallthrough".

Fixes: 997153b9a75c ("csky: Add flush_icache_mm to defer flush icache all")
Fixes: 0679d29d3e23 ("csky: fix syscache.c fallthrough warning")
Acked-by: Randy Dunlap <[e-mail]>
Co-Developed-by: Randy Dunlap <[e-mail]>
Signed-off-by: Guo Ren <[e-mail]>
Cc: Arnd Bergmann <[e-mail]>

arch/csky/mm/syscache.c

···
 		int, cache)
 {
 	switch (cache) {
-	case ICACHE:
 	case BCACHE:
-		flush_icache_mm_range(current->mm,
-				(unsigned long)addr,
-				(unsigned long)addr + bytes);
-		fallthrough;
 	case DCACHE:
 		dcache_wb_range((unsigned long)addr,
+				(unsigned long)addr + bytes);
+		if (cache != BCACHE)
+			break;
+		fallthrough;
+	case ICACHE:
+		flush_icache_mm_range(current->mm,
+				(unsigned long)addr,
 				(unsigned long)addr + bytes);
 		break;
 	default: