unit test: match wolfBoot_get_dts_size mock to the 2-arg signature

95227f82 (fdt: rewrite device tree parser with capacity bound and full
validation) changed wolfBoot_get_dts_size() to take a capacity argument
but left the mock in unit-update-disk-fs.c with the old 1-arg
signature, so the test no longer compiles (conflicting types). Update
the mock; behavior is unchanged (always -1, no DTS in this test).

tools/unit-tests/unit-update-disk-fs.c

@@ -682,9 +682,10 @@ uint32_t wolfBoot_get_blob_version(uint8_t *blob)
     return version;
 }
 
-int wolfBoot_get_dts_size(void *dts_addr)
+int wolfBoot_get_dts_size(void *dts_addr, uint32_t capacity)
 {
     (void)dts_addr;
+    (void)capacity;
     return -1;
 }