intel post-car: Increase stacktop alignment

Align top of stack to 8 bytes, value documented as FSP1.1 requirement.
Also fix some cases of uintptr_t casted to unsigned long.

Change-Id: I5bbd100eeb673417da205a2c2c3410fef1af61f0
Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-on: https://review.coreboot.org/17461
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Tested-by: build bot (Jenkins)
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>

src/lib/romstage_stack.c

@@ -44,5 +44,8 @@ uintptr_t romstage_ram_stack_top(void)
 	uintptr_t stack_top = romstage_ram_stack_base(ROMSTAGE_RAM_STACK_SIZE,
 		ROMSTAGE_STACK_CBMEM);
 	stack_top += ROMSTAGE_RAM_STACK_SIZE;
+
+	/* Make it aligned to a 8-byte boundary. */
+	stack_top = ALIGN_DOWN(stack_top, 8);
 	return stack_top;
 }