Split MAYBE_STATIC to _BSS and _NONZERO variants

These are required to cover the absensce of .data and
.bss sections in some programs, most notably ARCH_X86
in execute-in-place with cache-as-ram.

Change-Id: I80485ebac94b88c5864a949b17ad1dccdfda6a40
Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/35003
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Julius Werner <jwerner@chromium.org>

src/soc/intel/baytrail/northcluster.c

@@ -64,7 +64,7 @@
 
 uint32_t nc_read_top_of_low_memory(void)
 {
-	MAYBE_STATIC uint32_t tolm = 0;
+	MAYBE_STATIC_BSS uint32_t tolm = 0;
 
 	if (tolm)
 		return tolm;

src/soc/intel/braswell/northcluster.c

@@ -71,7 +71,7 @@
 
 uint32_t nc_read_top_of_low_memory(void)
 {
-	MAYBE_STATIC uint32_t tolm = 0;
+	MAYBE_STATIC_BSS uint32_t tolm = 0;
 
 	if (tolm)
 		return tolm;