To move forward and remove use of Kconfig in dts files lets just create
SoC specific dtsi files that the boards can include. This lets us
remove:
CONFIG_SOC_NRF51822_QFAA
CONFIG_SOC_NRF51822_QFAB
CONFIG_SOC_NRF51822_QFAC
CONFIG_SOC_NRF52810_QFAA
CONFIG_SOC_NRF52832_QFAA
CONFIG_SOC_NRF52832_CIAA
CONFIG_SOC_NRF52832_QFAB
CONFIG_SOC_NRF52840_QIAA
Signed-off-by: Kumar Gala <kumar.gala@linaro.org>