arch/x86/car.ld: Rename suffix _start/_end

This is more in line with how linker symbol for regions are defined.

Change-Id: I0bd7ae59a27909ed0fd38e6f7193816cb57e76af
Signed-off-by: Arthur Heymans <arthur@aheymans.xyz>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/36695
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>

src/soc/intel/quark/bootblock/esram_init.S

@@ -502,7 +502,7 @@ L44:
 	*/
 
 	/* Setup bootblock stack */
-	movl	$_car_stack_end, %esp
+	movl	$_ecar_stack, %esp
 
 before_carstage:
 	post_code(0x2b)