mips: mm: Discard ioremap_cacheable_cow() method

This macro substitution is the shortcut to map cacheable IO memory
with coherent and write-back attributes. Since it is entirely unused
by kernel, lets just remove it.
Signed-off-by: Serge Semin <fancer.lancer@gmail.com>
Signed-off-by: Paul Burton <paul.burton@mips.com>
Suggested-by: Christoph Hellwig <hch@infradead.org>
Patchwork: https://patchwork.linux-mips.org/patch/19937/
CC: Paul Burton <paul.burton@mips.com>
Cc: James Hogan <jhogan@kernel.org>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Sinan Kaya <okaya@codeaurora.org>
Cc: Huacai Chen <chenhc@lemote.com>
Cc: Sergey.Semin@t-platforms.ru
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org

arch/mips/include/asm/io.h

@@ -300,13 +300,6 @@ static inline void __iomem * __ioremap_mode(phys_addr_t offset, unsigned long si
 #define ioremap_wc(offset, size)					\
 	__ioremap_mode((offset), (size), boot_cpu_data.writecombine)
 
-/*
- * This is a MIPS specific ioremap variant. ioremap_cacheable_cow
- * requests a cachable mapping with CWB attribute enabled.
- */
-#define ioremap_cacheable_cow(offset, size)				\
-	__ioremap_mode((offset), (size), _CACHE_CACHABLE_COW)
-
 static inline void iounmap(const volatile void __iomem *addr)
 {
 	if (plat_iounmap(addr))