spi: omap3: Move headers code inside the driver

spi: omap3: Move headers code inside the driver

Header file have macro's and register definition and some unneeded
function proto types which becomes tunned further in future patches
and entire driver code resides in one file for more readability.

Cc: Tom Rini <trini@konsulko.com>
Cc: Simon Glass <sjg@chromium.org>
Signed-off-by: Jagan Teki <jteki@openedev.com>
[Fixes on code styles, Remove omap3_spi_txrx|write|read in header]
Signed-off-by: Christophe Ricard <christophe-h.ricard@st.com>