delay: collect {m, n, u}delay declarations to include/linux/delay.h

Currently, mdelay() and udelay() are declared in include/common.h,
while ndelay() in include/linux/compat.h.  It would be nice to
collect them into include/linux/delay.h like Linux.

While we are here, fix the ndelay() implementation; I used the
DIV_ROUND_UP() instead of (x)/1000 because it must wait *longer*
than the given period of time.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/include/linux/delay.h b/include/linux/delay.h
new file mode 100644
index 0000000..3dcd435
--- /dev/null
+++ b/include/linux/delay.h
@@ -0,0 +1,24 @@
+/*
+ * SPDX-License-Identifier:	GPL-2.0+
+ */
+
+#ifndef _LINUX_DELAY_H
+#define _LINUX_DELAY_H
+
+#include <linux/kernel.h>
+
+void __udelay(unsigned long usec);
+void udelay(unsigned long usec);
+
+static inline void mdelay(unsigned long msec)
+{
+	while (msec--)
+		udelay(1000);
+}
+
+static inline void ndelay(unsigned long nsec)
+{
+	udelay(DIV_ROUND_UP(nsec, 1000));
+}
+
+#endif /* defined(_LINUX_DELAY_H) */