lib: Add rp2040 build files

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>

lib/rp2040/cmsis_include/system_RP2040.h

@@ -0,0 +1,65 @@
+/*************************************************************************//**
+ * @file     system_RP2040.h
+ * @brief    CMSIS-Core(M) Device Peripheral Access Layer Header File for
+ *           Device RP2040
+ * @version  V1.0.0
+ * @date     5. May 2021
+ *****************************************************************************/
+/*
+ * Copyright (c) 2009-2021 Arm Limited. All rights reserved.
+ * Copyright (c) 2020 Raspberry Pi (Trading) Ltd.
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * Licensed under the Apache License, Version 2.0 (the License); you may
+ * not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an AS IS BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#ifndef _CMSIS_SYSTEM_RP2040_H
+#define _CMSIS_SYSTEM_RP2040_H
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+  \brief Exception / Interrupt Handler Function Prototype
+*/
+typedef void(*VECTOR_TABLE_Type)(void);
+
+/**
+  \brief System Clock Frequency (Core Clock)
+*/
+extern uint32_t SystemCoreClock;
+
+/**
+  \brief Setup the microcontroller system.
+
+   Initialize the System and update the SystemCoreClock variable.
+ */
+extern void SystemInit (void);
+
+
+/**
+  \brief  Update SystemCoreClock variable.
+
+   Updates the SystemCoreClock with current core Clock retrieved from cpu registers.
+ */
+extern void SystemCoreClockUpdate (void);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* _CMSIS_SYSTEM_RP2040_H */