clocksource: sh_mtu2: Drop incorrect SoC family name

The MTU2 hardware block is found in many Renesas SH and ARM SoCs, but
not in R-Car.
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>

Documentation/devicetree/bindings/timer/renesas,mtu2.txt

-* Renesas R-Car Multi-Function Timer Pulse Unit 2 (MTU2)
+* Renesas Multi-Function Timer Pulse Unit 2 (MTU2)
 
 The MTU2 is a multi-purpose, multi-channel timer/counter with configurable
 clock inputs and programmable compare match.