esp8266/mpconfigport_512k: Disable framebuf module for 512k build.

The 512k build recently overflowed because of the newly-enabled uselect
module.  uselect is arguable more important than framebuf for small
devices so we disable framebuf to keep the 512k build within its limit.

esp8266/mpconfigport_512k.h

@@ -17,3 +17,6 @@
 #define MICROPY_PY_BUILTINS_SLICE_ATTRS (0)
 #undef MICROPY_PY_ALL_SPECIAL_METHODS
 #define MICROPY_PY_ALL_SPECIAL_METHODS  (0)
+
+#undef MICROPY_PY_FRAMEBUF
+#define MICROPY_PY_FRAMEBUF             (0)