contrib: Add spaces around operator

I am reading contrib related code and found some style problems while
check the code using checkpatch.pl. This commit fixs the issue below:
ERROR: spaces required around that '*'

Signed-off-by: zhouyang <zhouyang789@huawei.com>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20210118031004.1662363-4-zhouyang789@huawei.com>
Message-Id: <20210213130325.14781-7-alex.bennee@linaro.org>

contrib/ivshmem-server/main.c

@@ -17,7 +17,7 @@
 #define IVSHMEM_SERVER_DEFAULT_PID_FILE       "/var/run/ivshmem-server.pid"
 #define IVSHMEM_SERVER_DEFAULT_UNIX_SOCK_PATH "/tmp/ivshmem_socket"
 #define IVSHMEM_SERVER_DEFAULT_SHM_PATH       "ivshmem"
-#define IVSHMEM_SERVER_DEFAULT_SHM_SIZE       (4*1024*1024)
+#define IVSHMEM_SERVER_DEFAULT_SHM_SIZE       (4 * 1024 * 1024)
 #define IVSHMEM_SERVER_DEFAULT_N_VECTORS      1
 
 /* used to quit on signal SIGTERM */