For system PMIC MC13892, you can select which LDO regulators to turn OFF when the system enters standby mode by setting VxSTBY bit in Regulator Mode 0 (reg 32) and Mode 1 (reg 33) registers.
In BSP, register masks REG_MODE_0_ALL_MASK and REG_MODE_1_ALL_MASK are defined in linux/arch/arm/mach-mx5/mx50_rdp_pmic_mc13892.c (mx50_arm2_pmic_mc13892.c for MX50 ARM2 configuration) and they will assign to MC13892 Regulator Mode 0 and Mode 1 registers during kernel startup.
If you want to keep the LDO power rail in standby mode, remove its bit mask from REG_MODE_x_ALL_MASK. Else, add its bit mask to REG_MODE_x_ALL_MASK to off the LDO power rail.
The regulator swtiching is automatically controlled by the external STANDBY pin to MC13892 from the system.