Update Linux to v5.4.2

Change-Id: Idf6911045d9d382da2cfe01b1edff026404ac8fd
diff --git a/arch/mips/mm/cache.c b/arch/mips/mm/cache.c
index 70a5231..33b4093 100644
--- a/arch/mips/mm/cache.c
+++ b/arch/mips/mm/cache.c
@@ -47,7 +47,6 @@
 EXPORT_SYMBOL_GPL(__flush_kernel_vmap_range);
 
 /* MIPS specific cache operations */
-void (*flush_cache_sigtramp)(unsigned long addr);
 void (*local_flush_data_cache_page)(void * addr);
 void (*flush_data_cache_page)(unsigned long addr);
 void (*flush_icache_all)(void);
@@ -63,8 +62,6 @@
 void (*_dma_cache_wback)(unsigned long start, unsigned long size);
 void (*_dma_cache_inv)(unsigned long start, unsigned long size);
 
-EXPORT_SYMBOL(_dma_cache_wback_inv);
-
 #endif /* CONFIG_DMA_NONCOHERENT */
 
 /*
@@ -76,7 +73,7 @@
 {
 	if (bytes == 0)
 		return 0;
-	if (!access_ok(VERIFY_WRITE, (void __user *) addr, bytes))
+	if (!access_ok((void __user *) addr, bytes))
 		return -EFAULT;
 
 	__flush_icache_user_range(addr, addr + bytes);