sh: fix sys_cacheflush error checking

sys_cacheflush should return with EINVAL if the cache parameter is not
one of ICACHE, DCACHE or BCACHE.
So, we need to include 0 in the first check.

It also adds the three definitions above as wrapper of the existent macros.

PS: ltp cacheflush01 test now passes.

Signed-off-by: Giuseppe Cavallaro <peppe.cavallaro@st.com>
Signed-off-by: Stuart Menefy <stuart.menefy@st.com>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>

arch/sh/include/asm/cachectl.h

@@ -9,4 +9,11 @@
 
 #define CACHEFLUSH_I		0x4
 
+/*
+ * Options for cacheflush system call
+ */
+#define ICACHE	CACHEFLUSH_I		/* flush instruction cache */
+#define DCACHE	CACHEFLUSH_D_PURGE	/* writeback and flush data cache */
+#define BCACHE	(ICACHE|DCACHE)		/* flush both caches */
+
 #endif /* _SH_CACHECTL_H */