media: dvb: Fix debug-fs statistics for SDMX

The number of packets processed by SDMX was not
set correctly to the actual number of bytes that
were read by SDMX. SDMX may not read the whole data
sent to it in case of memory playback in PULL mode.

Change-Id: Ic9ba6d52ff9b710bedafbbce5cdc033d05b1cf9f
Signed-off-by: Hamad Kadmany <hkadmany@codeaurora.org>