This reverts commit e87882eb.

According to the R-Car Gen3 Hardware Manual Errata for Rev 1.00 of Aug
24, 2018, the SEL_SSI2_{0,1} definition was to be deleted.  However,
this errata merely fixed an accidental double definition in the Hardware
User's Manual Rev. 1.00.  The real definition is still present in later
revisions of the manual (Rev. 1.50 and Rev. 2.00).

Hence revert the commit to recover the definition.

Based on a patch in the BSP by Takeshi Kihara
<takeshi.kihara.df@renesas.com>.
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Simon Horman <horms+renesas@verge.net.au>
Link: https://lore.kernel.org/r/20190904121658.2617-3-geert+renesas@glider.be