[gdb/build] Fix enum param_types odr violation

[gdb/build] Fix enum param_types odr violation

When building gdb with -O2 -flto, I run into:
...
gdb/guile/scm-param.c:121:6: warning: type 'param_types' violates the C++ \
  One Definition Rule [-Wodr]
 enum param_types
      ^
gdb/python/py-param.c:33:6: note: an enum with different value name is \
  defined in another translation unit
 enum param_types
      ^
...

Fix this by renaming to enum scm_param_types and py_param_types.

Tested on x86_64-linux.

Approved-By: Tom Tromey <tom@tromey.com>
PR build/22395
Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=22395