ARM: dts: owl-s500-roseapplepi: Add ATC2603C PMIC

Add device tree node for ATC2603C PMIC and remove the 'fixed-3.1V'
dummy regulator used for the uSD supply.

Additionally, add 'SYSPWR' fixed regulator and provide cpu0 supply.

Signed-off-by: Cristian Ciocaltea <cristian.ciocaltea@gmail.com>
Signed-off-by: Manivannan Sadhasivam <mani@kernel.org>
Reviewed-by: Manivannan Sadhasivam <mani@kernel.org>
Link: https://lore.kernel.org/r/2e0a2931ae3757f016948e7c78e8e54afa325ae0.1615538629.git.cristian.ciocaltea@gmail.com
Link: https://lore.kernel.org/r/20210408062232.3575-1-mani@kernel.org

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Signed-off-by: Arnd Bergmann <arnd@arndb.de>