PCI: rcar: Use proper name for the R-Car SoC

It is 'R-Car', not 'RCar'. No code or binding changes, only descriptive
text.

Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Geert Uytterhoeven <geert+renesas@glider.be>
Acked-by: Simon Horman <horms+renesas@verge.net.au>