ARM: davinci: da8xx_register_spi() should not register SPI board info

ARM: davinci: da8xx_register_spi() should not register SPI board info

Without this patch, da8xx_register_spi() registers the SPI board info,
the SPI controller, and sets its number of chipselect to the size of the
static spi_board_info array. This is bad because a SPI board info may
declare devices for different SPI buses, and because other code can also
call spi_register_board_info() (e.g. a daughter board might provide
additional SPI devices).

This patch removes the spi_register_board_info() call from
da8xx_register_spi(), renames this last one to da8xx_register_spi_bus()
to be more explicit, takes the number of chipselect as a function
parameter, and updates the impacted board-da8{3,5}0-evm.c, and
board-mityomapl138.c files accordingly. It also sets the SPI platform
data static, as it doesn't need to be exported.

Signed-off-by: Vivien Didelot <vivien.didelot@savoirfairelinux.com>
[nsekhar@ti.com: fixed conflicts with v3.7-rc7, converted to use pr_warn(),
modified print messages to use __func__]
Signed-off-by: Sekhar Nori <nsekhar@ti.com>