linux-user/syscall.c: malloc to g_try_malloc

Use g_try_malloc instead of malloc to alocate the target ifconfig.
Also replace the corresponding free with g_free.

Signed-off-by: Ahmed Abouzied <email@aabouzied.com>
Message-Id: <20220104143841.25116-1-email@aabouzied.com>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>