scons: rename PIPE_SUBSYSTEM_EMBEDDED to EMBEDDED_DEVICE

It has nothing to do with the PIPE_SUBSYSTEM_* stuff from gallium.

Signed-off-by: Eric Engestrom <eric.engestrom@intel.com>
Reviewed-by: Matt Turner <mattst88@gmail.com>

src/util/u_debug.c

@@ -51,7 +51,7 @@ void
 _debug_vprintf(const char *format, va_list ap)
 {
    static char buf[4096] = {'\0'};
-#if defined(PIPE_OS_WINDOWS) || defined(PIPE_SUBSYSTEM_EMBEDDED)
+#if defined(PIPE_OS_WINDOWS) || defined(EMBEDDED_DEVICE)
    /* We buffer until we find a newline. */
    size_t len = strlen(buf);
    int ret = vsnprintf(buf + len, sizeof(buf) - len, format, ap);