spi: davinci: kconfig: add manufacturer name to prompt string

Add manufacturer name to the Kconfig prompt string and move
the controller name to the begining of the prompt.

This helps locate the driver easily among the list of existing
drivers.

While at it, also add information about being able to build
the driver as module.

Tested-By: Brian Niebuhr <bniebuhr@efjohnson.com>
Signed-off-by: Sekhar Nori <nsekhar@ti.com>