Fix SerialUART RP2350B define checks

Fixes #2460

Author: earlephilhower

cores/rp2040/SerialUART.cpp

@@ -32,7 +32,7 @@ extern void serialEvent1() __attribute__((weak));
 extern void serialEvent2() __attribute__((weak));
 
 bool SerialUART::setRX(pin_size_t pin) {
-#ifdef RP2350B
+#ifdef PICO_RP2350B
     constexpr uint64_t valid[2] = { __bitset({1, 13, 17, 29, 33, 45}) /* UART0 */,
                                     __bitset({5, 9, 21, 25, 37, 41})  /* UART1 */
                                   };
@@ -59,7 +59,7 @@ bool SerialUART::setRX(pin_size_t pin) {
 }
 
 bool SerialUART::setTX(pin_size_t pin) {
-#ifdef RP2350B
+#ifdef PICO_RP2350B
     constexpr uint64_t valid[2] = { __bitset({0, 12, 16, 28, 32, 44}) /* UART0 */,
                                     __bitset({4, 8, 20, 24, 36, 40})  /* UART1 */
                                   };
@@ -86,7 +86,7 @@ bool SerialUART::setTX(pin_size_t pin) {
 }
 
 bool SerialUART::setRTS(pin_size_t pin) {
-#ifdef RP2350B
+#ifdef PICO_RP2350B
     constexpr uint64_t valid[2] = { __bitset({3, 15, 19, 31, 35, 47}) /* UART0 */,
                                     __bitset({7, 11, 23, 27, 39, 43})  /* UART1 */
                                   };
@@ -113,7 +113,7 @@ bool SerialUART::setRTS(pin_size_t pin) {
 }
 
 bool SerialUART::setCTS(pin_size_t pin) {
-#ifdef RP2350B
+#ifdef PICO_RP2350B
     constexpr uint64_t valid[2] = { __bitset({2, 14, 18, 30, 34, 46}) /* UART0 */,
                                     __bitset({6, 10, 22, 26, 38, 42})  /* UART1 */
                                   };