utx8245: fix build breakage due to assert()

Commit 21726a7a "Add assert() for debug assertions" broke building the
utx8245 board:

dlmalloc.c: In function 'do_check_chunk':
dlmalloc.c:1660: error: 'sz' undeclared (first use in this function)
dlmalloc.c:1660: error: (Each undeclared identifier is reported only once
dlmalloc.c:1660: error: for each function it appears in.)
dlmalloc.c: In function 'do_check_free_chunk':
dlmalloc.c:1689: error: 'next' undeclared (first use in this function)
dlmalloc.c: In function 'do_check_malloced_chunk':
dlmalloc.c:1748: error: 'sz' undeclared (first use in this function)
dlmalloc.c:1750: error: 'room' undeclared (first use in this function)

Signed-off-by: Wolfgang Denk <wd@denx.de>
Cc: Simon Glass <sjg@chromium.org>