dts/bindings: Add reset and irq gpios to "st,spbtle-rf" yaml

In order to generate GPIO definition for control pin of BlueNRG module
define reset-gpio and irq-gpio in st,spbtle-rf yaml binding.

Add HAS_DTS_SPI_PINS kconfig symbol to control use of the '#define'

Signed-off-by: Erwan Gouriou <erwan.gouriou@linaro.org>