CONFIG_MACH_BERLIN_BG2 is not available for thedefaultarchitecture x86.
Result is shown for architecture arm

Marvell Armada 1500 (BG2)

modulename: bg2.ko

configname: CONFIG_MACH_BERLIN_BG2

Linux Kernel Configuration
└─>Marvell Berlin SoCs
└─>Marvell Armada 1500 (BG2)
In linux kernel since version 3.10 (release Date: 2013-06-30)  
source code:
drivers/clk/berlin/bg2.c