dvb: fix build errors on macosx

dvb: fix build errors on macosx

fixes the following compile errors:

cc1: warnings being treated as errors
camswclient.c: In function 'cam_sw_client_open':
camswclient.c:81: warning: implicit declaration of function 'strncpy'
camswclient.c:81: warning: incompatible implicit declaration of built-in function 'strncpy'
camswclient.c:89: warning: implicit declaration of function 'strerror'
camswclient.c:89: warning: nested extern declaration of 'strerror'
camswclient.c:89: warning: format '%s' expects type 'char *', but argument 9 has type 'int'
camswclient.c: In function 'send_ca_pmt':
camswclient.c:129: warning: implicit declaration of function 'memcpy'
camswclient.c:129: warning: incompatible implicit declaration of built-in
function 'memcpy'

gstdvbsrc.c:48:19: error: error.h: No such file or directory

Signed-off-by: Rob Clark <rob@ti.com>