arm64: dts: imx8mq-librem5-devkit: Tweak pmic regulators

arm64: dts: imx8mq-librem5-devkit: Tweak pmic regulators

BUCK3 needs a regulator-enable-ramp-delay since otherwise the board
freezes on etnaviv probe. With this pgc_gpu suspends and resumes as
expected. This must have been always broken since gpcv2 support was
enabled.

We also enable all the regulators needed for Deep Sleep Mode (DSM) as
always-on:

- VDD_SOC supplied by BUCK1
- VDDA_1P8 supplied by BUCK7
- VDDA_0P9 supplied by LDO4
- VDDA_DRAM supplied by LDO3
- NVCC_DRAM supplied by BUCK8
- VDD_DRAM supplied by BUCK5

Finally LDO5 and LDO6 provide VDD_PHY_1V8 and VDD_PHY_0V9 used by the
SOCs MIPI, HDMI and USB IP cores. While we would in theory be able to
turn these off (and I've tested that or LDO6 and mipi with USB disabled)
it is of little practical use atm since USB doesn't runtime suspend so
let's revisit this at a later point.

Signed-off-by: Guido Günther <agx@sigxcpu.org>
Reviewed-by: Krzysztof Kozlowski <krzk@kernel.org>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>