generic: Create generic board infrastructure and move misc.h to it

Instead of creating a misc.h file in each board directory, create a
generic board directory and declare misc.h there.

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

src/generic/misc.h

@@ -0,0 +1,16 @@
+#ifndef __GENERIC_MISC_H
+#define __GENERIC_MISC_H
+
+#include <stddef.h> // size_t
+#include <stdint.h> // uint8_t
+
+char *console_get_input(uint8_t *plen);
+void console_pop_input(uint8_t len);
+char *console_get_output(uint8_t len);
+void console_push_output(uint8_t len);
+
+size_t alloc_maxsize(size_t reqsize);
+
+uint16_t crc16_ccitt(char *buf, uint8_t len);
+
+#endif // misc.h