soc: qcom: Remove redundant bootstats

'bootloader_load_kernel' and 'bootloader_chksum_time' are
redundant information. As the entries in IMEM have a limit
(as of now 8 entries), recreate them from *_start and *_done
variants, which are populated from the bootloader.

Change-Id: I4794cd5665a7593aca94542fd759fbd0da068d96
Signed-off-by: Shreyas K K <shrekk@codeaurora.org>