egl-static: fix printf warning

egl-static: fix printf warning

Noticed by clang:

egl_st.c:57:50: warning: field precision should have type 'int',
but argument has type 'size_t' (aka 'unsigned long') [-Wformat]
      ret = util_snprintf(path, sizeof(path), "%.*s/%s" UTIL_DL_EXT,
                                               ~~^~

NOTE: This is a candidate for the 8.0 branch.

Reviewed-by: Brian Paul <brianp@vmware.com>