CorebootPayloadPkg DSC: Change the section alignment option

The current CorebootPayloadPkg will print the following message
"InsertImageRecord - Section Alignment(0x20) is not 4K" during
boot. It is caused by the section alignment arranged by the linker.
This patch change the alignment to 4K for runtime drivers.

Cc: Prince Agyeman <prince.agyeman@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Maurice Ma <maurice.ma@intel.com>
Reviewed-by: Prince Agyeman <prince.agyeman@intel.com>