xtest: regression_1000: remove unneeded stat.h include

Hack to work around musl compile error:
 In file included from optee-test/3.17.0-r0/recipe-sysroot/usr/include/sys/stat.h:23,
                  from optee-test/3.17.0-r0/git/host/xtest/regression_1000.c:25:
 optee-test/3.17.0-r0/recipe-sysroot/usr/include/bits/stat.h:17:26: error: expected identifier or '(' before '[' token
    17 |         unsigned __unused[2];
       |                          ^

stat.h is not needed, since it is not being used in this file.  So removing it.

Signed-off-by: Jon Mason <jon.mason@arm.com>
Reviewed-by: Jerome Forissier <jerome.forissier@linaro.org>
Acked-by: Jens Wiklander <jens.wiklander@linaro.org>

host/xtest/regression_1000.c

@@ -24,7 +24,6 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
-#include <sys/stat.h>
 #include <sys/types.h>
 #include <ta_arm_bti.h>
 #include <ta_concurrent.h>