sparsemem support on MIPS

[naveen yadav <yad.naveen@gmail.com>]

 Dear all,

I build MIPS 32 with sparsemem support to take care of holes in
physical memory, this conserve memory but put overhead to speed
because of pointer redirection in pfn_to_page().

To prevent this conversion I tried to use
CONFIG_SPARSEMEM_VMEMMAP_ENABLE on MIPS 32 but kernel build fails
becauase most of the supported functions related to vmemmap are
supported for 64 bit architectures only.

I wish to compare memory and speed result with / without
CONFIG_SPARSEMEM_VMEMMAP_ENABLE in MIPS 32. I need your comment in it
?

Thanks