feat: enable multicore support for RP2040

Add LIB_PICO_MULTICORE=1 flag to enable multicore support.

Author: Goran Miskovic

tools/libpico/CMakeLists.txt

@@ -51,6 +51,7 @@ if (${cpu} MATCHES "rp2040")
         PICO_XOSC_STARTUP_DELAY_MULTIPLIER=64
         PICO_FLOAT_SUPPORT_ROM_V1=1
         PICO_DOUBLE_SUPPORT_ROM_V1=1
+        LIB_PICO_MULTICORE=1
         PICO_RP2040=1)
 elseif (${cpu} MATCHES "rp2350")
     set(xcd