pfuze: Fix the pmic_get() parameter in the DM case

Currently the following hang is observed when booting a imx6sx-sdb
board:

U-Boot 2020.01-rc5-00004-g643366bcd5 (Dec 19 2019 - 14:56:23 -0300)

CPU:   Freescale i.MX6SX rev1.0 996 MHz (running at 792 MHz)
CPU:   Extended Commercial temperature grade (-20C to 105C) at 32C
Reset cause: POR
Model: Freescale i.MX6 SoloX SDB RevB Board
Board: MX6SX SABRE SDB revA
DRAM:  1 GiB
initcall sequence bffd8514 failed at call 87804cc0 (err=-19)
### ERROR ### Please RESET the board ###

When pmic_get() is used with DM the first parameter must be
the complete node name plus the unit address.

Fix the pmic_get() parameter to fix the boot regression.

Tested on a imx6sx-sdb and imx6q-sabresd boards.

Signed-off-by: Fabio Estevam <festevam@gmail.com>
Reviewed-by: Igor Opaniuk <igor.opaniuk@toradex.com>