filesrc: set default block size from local define
filesrc: set default block size from local define

Doesn't actually change the default value, just makes use of the
define there is. Superficial testing with fakesink and jpegdec did
not reveal improved performance for bigger block sizes, so leave
default as it is.

lubosz/gstreamer,cfoch/gstreamer,shelsonjava/gstreamer,krieger-od/gstreamer,jpxiong/gstreamer,jpxiong/gstreamer,surround-io/gstreamer,collects/gstreamer,lubosz/gstreamer,Lachann/gstreamer,jpxiong/gstreamer,collects/gstreamer,drothlis/gstreamer,cablelabs/gstreamer,drothlis/gstreamer,justinjoy/gstreamer,shelsonjava/gstreamer,Lachann/gstreamer,cfoch/gstreamer,ensonic/gstreamer,justinjoy/gstreamer,collects/gstreamer,jpakkane/gstreamer,lubosz/gstreamer,mparis/gstreamer,mparis/gstreamer,mparis/gstreamer,justinjoy/gstreamer,lovebug356/gstreamer,surround-io/gstreamer,surround-io/gstreamer,Lachann/gstreamer,collects/gstreamer,shelsonjava/gstreamer,StreamUtils/gstreamer,krichter722/gstreamer,cablelabs/gstreamer,shelsonjava/gstreamer,lovebug356/gstreamer,ensonic/gstreamer,shelsonjava/gstreamer,jpxiong/gstreamer,jpakkane/gstreamer,lovebug356/gstreamer,surround-io/gstreamer,cfoch/gstreamer,lubosz/gstreamer,centricular/gstreamer,ensonic/gstreamer,krieger-od/gstreamer,ensonic/gstreamer,justinjoy/gstreamer,krichter722/gstreamer,Lachann/gstreamer,krieger-od/gstreamer,mparis/gstreamer,krichter722/gstreamer,krichter722/gstreamer,justinjoy/gstreamer,cablelabs/gstreamer,StreamUtils/gstreamer,jpxiong/gstreamer,krieger-od/gstreamer,krieger-od/gstreamer,centricular/gstreamer,StreamUtils/gstreamer,ensonic/gstreamer,lovebug356/gstreamer,centricular/gstreamer,lubosz/gstreamer,drothlis/gstreamer,krichter722/gstreamer,cfoch/gstreamer,jpakkane/gstreamer,StreamUtils/gstreamer,cablelabs/gstreamer,jpakkane/gstreamer,jpakkane/gstreamer,cablelabs/gstreamer,Lachann/gstreamer,collects/gstreamer,centricular/gstreamer,centricular/gstreamer,cfoch/gstreamer,StreamUtils/gstreamer,lovebug356/gstreamer,drothlis/gstreamer,drothlis/gstreamer,surround-io/gstreamer,mparis/gstreamer