security/vboot: relocate and rename vboot_platform_is_resuming()

After measured boot is decoupled from verified boot in CB:35077,
vboot_platform_is_resuming() is never vboot-specific, thus it is
renamed to platform_is_resuming() and declared in bootmode.h.

Change-Id: I29b5b88af0576c34c10cfbd99659a5cdc0c75842
Signed-off-by: Bill XIE <persmule@hardenedlinux.org>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/39103
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Julius Werner <jwerner@chromium.org>

src/include/bootmode.h

@@ -29,4 +29,10 @@ int display_init_required(void);
 int gfx_get_init_done(void);
 void gfx_set_init_done(int done);
 
+/*
+ * Determine if the platform is resuming from suspend. Returns 0 when
+ * not resuming, > 0 if resuming, and < 0 on error.
+ */
+int platform_is_resuming(void);
+
 #endif /* __BOOTMODE_H__ */