include: configs: am64x_evm: Optimize size of SPL BSS

Current BSS allocation of SPL is as below:
size spl/u-boot-spl
   text	   data	    bss	    dec	    hex	filename
 144572	   5484	   1752	 151808	  25100	spl/u-boot-spl

But 20KB is allocated currently for BSS. Reduce it to 4KB and
save some space for stack.

Signed-off-by: Lokesh Vutla <lokeshvutla@ti.com>
1 file changed