Baikal-T1 Boot ROMs OF-based physical memory map handling

configname: CONFIG_MTD_PHYSMAP_BT1_ROM

Linux Kernel Configuration
└─>Device Drivers
└─>Memory Technology Device (MTD) support
└─>Mapping drivers for chip access
└─>Baikal-T1 Boot ROMs OF-based physical memory map handling
In linux kernel since version 5.1 (release Date: 2019-05-05)  
This provides some extra DT physmap parsing for the Baikal-T1
platforms, some detection and setting up ROMs-specific accessors.