soc: tegra: Move powergate-bpmp driver to the genpd dir

To simplify with maintenance let's move the powergate-bpmp driver to the
new genpd directory. Going forward, patches are intended to be managed
through a separate git tree, according to MAINTAINERS.

Note that, we leave the pmc driver in the soc directory for now, as it
looks like it may need some re-structuring before it's ready to be moved.

Cc: Thierry Reding <[e-mail]>
Cc: Jonathan Hunter <[e-mail]>
Cc: Mikko Perttunen <[e-mail]>
Cc: <[e-mail]>
Acked-by: Thierry Reding <[e-mail]>
Signed-off-by: Ulf Hansson <[e-mail]>

drivers/genpd/Makefile

···
 obj-y					+= samsung/
 obj-y					+= starfive/
 obj-y					+= sunxi/
+obj-y					+= tegra/

drivers/genpd/tegra/Makefile

···
+# SPDX-License-Identifier: GPL-2.0
+obj-$(CONFIG_SOC_TEGRA_POWERGATE_BPMP)	+= powergate-bpmp.o

drivers/soc/tegra/Makefile

···
 obj-y += common.o
 obj-$(CONFIG_SOC_TEGRA_FLOWCTRL) += flowctrl.o
 obj-$(CONFIG_SOC_TEGRA_PMC) += pmc.o
-obj-$(CONFIG_SOC_TEGRA_POWERGATE_BPMP) += powergate-bpmp.o
 obj-$(CONFIG_SOC_TEGRA20_VOLTAGE_COUPLER) += regulators-tegra20.o
 obj-$(CONFIG_SOC_TEGRA30_VOLTAGE_COUPLER) += regulators-tegra30.o
 obj-$(CONFIG_ARCH_TEGRA_186_SOC) += ari-tegra186.o