ntripclient: fix musl comaptibility

Add missing `sys/select.h` include to `ntripclient.c` to provide
declarations for `struct timeval` and `fd_set` under musl.

Signed-off-by: Jo-Philipp Wich <jow@openwrt.org>

net/ntripclient/patches/100-musl-compat.patch

@@ -0,0 +1,10 @@
+--- a/ntripclient.c
++++ b/ntripclient.c
+@@ -44,6 +44,7 @@
+   #include <fcntl.h>
+   #include <unistd.h>
+   #include <arpa/inet.h>
++  #include <sys/select.h>
+   #include <sys/socket.h>
+   #include <netinet/in.h>
+   #include <netdb.h>