fdsan: minor refactoring.

Make it easier for other code to parse the fdsan table themselves by
making it so that they can include the bionic_fdsan.h header to get a
struct definition with the layout without bringing in other
dependencies.

Test: treehugger
Change-Id: I3583ef113991234aa83cd193a4eb139ad06737c7
diff --git a/libc/private/bionic_globals.h b/libc/private/bionic_globals.h
index e569209..eee33c9 100644
--- a/libc/private/bionic_globals.h
+++ b/libc/private/bionic_globals.h
@@ -46,7 +46,7 @@
 
 // Globals shared between the dynamic linker and libc.so.
 struct libc_shared_globals {
-  FdTable<128> fd_table;
+  FdTable fd_table;
 };
 
 __LIBC_HIDDEN__ extern libc_shared_globals* __libc_shared_globals;