ARM: dts: alt: enable UHS for SDHI 0 & 1

Add the "1v8" pinctrl state and sd-uhs-sdr50 property to SDHI{0,1}.

Signed-off-by: Simon Horman <horms+renesas@verge.net.au>
Reviewed-by: Wolfram Sang <wsa+renesas@sang-engineering.com>