version: Remove global macro U_BOOT_VERSION_STRING from version.h

Version string is available in global variable char version_string[].
Macro U_BOOT_VERSION_STRING is not used by any other file, so remove it
completely from version.h. Other files were already converted to use
variable version_string[].

Signed-off-by: Pali Rohár <pali@kernel.org>
Reviewed-by: Tom Rini <trini@konsulko.com>
diff --git a/cmd/version.c b/cmd/version.c
index 2f9b898..130e31c 100644
--- a/cmd/version.c
+++ b/cmd/version.c
@@ -13,6 +13,9 @@
 #include <asm/cb_sysinfo.h>
 #endif
 
+#define U_BOOT_VERSION_STRING U_BOOT_VERSION " (" U_BOOT_DATE " - " \
+	U_BOOT_TIME " " U_BOOT_TZ ")" CONFIG_IDENT_STRING
+
 const char version_string[] = U_BOOT_VERSION_STRING;
 
 static int do_version(struct cmd_tbl *cmdtp, int flag, int argc,