linux_compat: handle __GFP_ZERO in kmalloc()

Currently, kzalloc() returns zero-filled memory, while kmalloc()
simply ignores the second argument and never fills the memory
area with zeros.

I want kmalloc(size, __GFP_ZERO) to behave as kzalloc() does,
which will make it easier to add more memory allocator variants.

With the introduction of __GFP_ZERO flag, going forward, kzmalloc()
variants can fall back to kmalloc() enabling the __GFP_ZERO flag.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Reviewed-by: Heiko Schocher <hs@denx.de>
Acked-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Lukasz Majewski <l.majewski@samsung.com>
diff --git a/lib/linux_compat.c b/lib/linux_compat.c
index 8c7a7b5..a936a7e 100644
--- a/lib/linux_compat.c
+++ b/lib/linux_compat.c
@@ -16,14 +16,13 @@
 
 void *kmalloc(size_t size, int flags)
 {
-	return memalign(ARCH_DMA_MINALIGN, size);
-}
+	void *p;
 
-void *kzalloc(size_t size, int flags)
-{
-	void *ptr = kmalloc(size, flags);
-	memset(ptr, 0, size);
-	return ptr;
+	p = memalign(ARCH_DMA_MINALIGN, size);
+	if (flags & __GFP_ZERO)
+		memset(p, 0, size);
+
+	return p;
 }
 
 struct kmem_cache *get_mem(int element_sz)