CONFIG_DYNAMIC_MEMSTART is not available for thedefaultarchitecture x86.
Result is shown for architecture powerpc

Enable page aligned dynamic load address for kernel


Linux Kernel Configuration
└─>Advanced setup
└─>Enable page aligned dynamic load address for kernel
In linux kernel since version 3.1 (release Date: 2011-10-24)  
This option enables the kernel to be loaded at any page aligned
physical address. The kernel creates a mapping from KERNELBASE to
the address where the kernel is loaded. The page size here implies
the TLB page size of the mapping for kernel on the particular platform.
Please refer to the init code for finding the TLB page size.

DYNAMIC_MEMSTART is an easy way of implementing pseudo-RELOCATABLE
kernel image, where the only restriction is the page aligned kernel
load address. When this option is enabled, the compile time physical
address CONFIG_PHYSICAL_START is ignored.

This option is overridden by CONFIG_RELOCATABLE