ARM: dts: ux500: Move generic pin configs out of ste-href-family-pinctrl.dtsi

All existing Ux500 boards make use of ste-href-family-pinctrl.dtsi,
which contains shared pin configurations for UART, I2C and SDI.
Most of these can be also used for devices not based on HREF.

Move the generic pin configs into a new device tree include
"ste-dbx5x0-pinctrl.dtsi". There is no functional change (yet),
as a next step we will rename the pin configs to use more generic
names.
Signed-off-by: Stephan Gerhold <stephan@gerhold.net>
Link: https://lore.kernel.org/r/20191125122256.53482-1-stephan@gerhold.netSigned-off-by: Linus Walleij <linus.walleij@linaro.org>