SoC: sdm845: find and save KASLR to env variables

KASLR address is needed to boot fully functional Android.
KASLR is set by primary bootloader, and since u-boot is used
as a secondary bootloader(replacing kernel) on sdm845 platform,
KASLR may be found by comparing memory chunks at relocaddr over
supposed KASLR range.

Signed-off-by: Dzmitry Sankouski <dsankouski@gmail.com>
Reviewed-by: Ramon Fried <rfried.dev@gmail.com>