id_ca: Fix build in big endian systems

[Ryzee119]

These variables look to be left over from the commit sulix@5ac988e

Easily missed as its wrapped in a CK_CROSS_IS_BIGENDIAN ifdef

id_ca.c:747:27: error: 'FON_MAINFONT' undeclared (first use in this function)
  747 |         else if (chunk >= FON_MAINFONT && chunk <= /*FON_WATCHFONT*/ FON_MAINFONT + 2)
      |                           ^~~~~~~~~~~~
id_ca.c:756:27: error: 'EXTERN_COMMANDER' undeclared (first use in this function)
  756 |         else if (chunk >= EXTERN_COMMANDER && chunk <= EXTERN_KEEN)
      |                           ^~~~~~~~~~~~~~~~
d_ca.c:756:56: error: 'EXTERN_KEEN' undeclared (first use in this function)
  756 |         else if (chunk >= EXTERN_COMMANDER && chunk <= EXTERN_KEEN)
      |                                                        ^~~~~~~~~~~