ARM64: dts: meson-gxbb-vega-s95: Add SD/SDIO/MMC and PWM nodes

All boards from the Tronsmart Vega S95 series are sharing similar MMC
based hardware.
sd_emmc_a is used to connect a Broadcom based SDIO wifi card (supported
by the brcmfmac driver). The 32.768KHz LPO clock for the wifi chip is
generated by PWM_E.
sd_emmc_b is routed to the SD-card. Unlike p20x there is no GPIO
regulator, meaning it only supports 3.3V (which seems to be hard-wired).
The eMMC chip is connected to sd_emmc_c and is implemented similar to
the meson-gxbb-p20x boards (meaning that hard-wired fixed regulators
are used).

Signed-off-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Signed-off-by: Kevin Hilman <khilman@baylibre.com>