symbols: Change implementation details of DECLARE_OPTIONAL_REGION()

It seems that GCC's LTO doesn't like the way we implement
DECLARE_OPTIONAL_REGION(). This patch changes it so that rather than
having a normal DECLARE_REGION() in <symbols.h> and then an extra
DECLARE_OPTIONAL_REGION() in the C file using it, you just say
DECLARE_OPTIONAL_REGION() directly in <symbols.h> (in place and instead
of the usual DECLARE_REGION()). This basically looks the same way in the
resulting object file but somehow LTO seems to like it better.

Signed-off-by: Julius Werner <jwerner@chromium.org>
Change-Id: I6096207b311d70c8e9956cd9406bec45be04a4a2
Reviewed-on: https://review.coreboot.org/c/coreboot/+/44791
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Jacob Garber <jgarber1@ualberta.ca>
Reviewed-by: Hung-Te Lin <hungte@chromium.org>
Reviewed-by: HAOUAS Elyes <ehaouas@noos.fr>

src/lib/bootblock.c

@@ -10,8 +10,6 @@
 #include <symbols.h>
 #include <timestamp.h>
 
-DECLARE_OPTIONAL_REGION(timestamp);
-
 __weak void bootblock_mainboard_early_init(void) { /* no-op */ }
 __weak void bootblock_soc_early_init(void) { /* do nothing */ }
 __weak void bootblock_soc_init(void) { /* do nothing */ }

src/lib/timestamp.c

@@ -11,8 +11,6 @@
 
 #define MAX_TIMESTAMPS 192
 
-DECLARE_OPTIONAL_REGION(timestamp);
-
 /* This points to the active timestamp_table and can change within a stage
    as CBMEM comes available. */
 static struct timestamp_table *glob_ts_table;