basecmd: Avoid calling malloc() from main code

Introduce a new board function alloc_chunk() to allocate dynamic
memory.  This allows the board code to implement memory allocations
without using the standard malloc() interface.

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

src/generic/misc.h

@@ -14,7 +14,8 @@ uint8_t timer_is_before(uint32_t time1, uint32_t time2);
 uint32_t timer_read_time(void);
 void timer_periodic(void);
 
-size_t alloc_maxsize(size_t reqsize);
+void *alloc_chunk(size_t size);
+void *alloc_chunks(size_t size, size_t count, size_t *avail);
 
 uint16_t crc16_ccitt(char *buf, uint8_t len);