test: mbr: Unmap the buffers after use

This tests maps some local variables into sandbox's address space. Make
sure to unmap them afterwards.

Note that the normal approach with sandbox is to use a fixed memory
address in the RAM, to avoid needing to create a map for transient local
variables.

Signed-off-by: Simon Glass <sjg@chromium.org>
Fixes: 04291ee0ab ("cmd: mbr: Allow 4 MBR partitions without need...")

test/cmd/mbr.c

@@ -456,6 +456,9 @@ static int mbr_test_run(struct unit_test_state *uts)
 			"5P EBR+0x%04X: expected %#02X, actual: %#02X\n",
 			ebr_cmp_start + i, ebr_parts_ref_p5[i], rbuf[ebr_cmp_start + i]);
 	}
+	unmap_sysmem(mbr_wbuf);
+	unmap_sysmem(ebr_wbuf);
+	unmap_sysmem(rbuf);
 
 	return 0;
 }