ARM: dts: cygnus: Add additional peripherals to dtsi

Add nodes for peripherals in Cygnus dtsi: sdhci, keypad, spi, dma,
pinmux configs.

Signed-off-by: Jonathan Richardson <jonathan.richardson@broadcom.com>
Signed-off-by: Scott Branden <scott.branden@broadcom.com>
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>