msm: ipa: Send actual DL flt rule length to Q6

Currently max length size of DL flt rule is
sent to Q6. But 64K memory allocation is not
always guranteed. Send actual size of DL flt rule
to Q6 to avoid memory error and install flt rule.

Change-Id: I5bb6d2d2b564d06c2f0521aaa2a3c54dc646f07e
Signed-off-by: Armaan Siddiqui <asiddiqu@codeaurora.org>