Adding/propage macros/signature typedefs for ROM functions. Make rom_func_lookup non-flash safe for flash functions (#586)

* add typedef signatures and ROM code defines for bootrom functions. Propogate uses thru SDK code. Add _inline version of rom_func_lookup

src/rp2_common/pico_float/float_init_rom.c

@@ -66,5 +66,5 @@ void __aeabi_float_init(void) {
         assert(*((uint8_t *)(rom_table-2)) * 4 >= SF_TABLE_V2_SIZE);
         memcpy(&sf_table, rom_table, SF_TABLE_V2_SIZE);
     }
-    sf_clz_func = rom_func_lookup(rom_table_code('L', '3'));
+    sf_clz_func = rom_func_lookup(ROM_FUNC_CLZ32);
 }