Make GPS navigation epochs interrupt-coherent

Wait for every navigation-ready tracking channel in a GPS epoch, remove unlocked channels without a timeout, and keep late joins for the next epoch. Reset PLIC ownership during warm initialization and extend Linux synthetic, integrity, and fake-MMIO regression coverage.

soc/software/gps_system/tests/fake_bsp/bsp/mmio.h

@@ -0,0 +1,19 @@
+#ifndef TEST_BSP_MMIO_H
+#define TEST_BSP_MMIO_H
+
+#include <stdint.h>
+
+uint32_t test_bsp_read32(uintptr_t address);
+void test_bsp_write32(uintptr_t address, uint32_t value);
+
+static inline uint32_t bsp_read32(uintptr_t address)
+{
+	return test_bsp_read32(address);
+}
+
+static inline void bsp_write32(uintptr_t address, uint32_t value)
+{
+	test_bsp_write32(address, value);
+}
+
+#endif