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

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>

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