power: Rename CONFIG_POWER_TPS65217 with CONFIG_PMIC_TPS65217

Up till now the CONFIG_POWER_TPS65217 has been defined in several header
files for am335x SoC.

This patch renames it to CONFIG_PMIC_TPS65217, which better reflects the
role of this IC circuit.

Moreover, new CONFIG_PMIC_TPS65217 has been introduced in Kconfig
to be used with boards, which both support DM_PMIC and DM_I2C.

Signed-off-by: Lukasz Majewski <lukma@denx.de>
Reviewed-by: Jaehoon Chung <jh80.chung@samsung.com>
[trini: Migrate all other platforms as well]
Signed-off-by: Tom Rini <trini@konsulko.com>