msm: eva: copy back the validated size in bytes properly

As performing a right shift and then a left shift does
not yield the same results, the validated size is copied back.

Change-Id: I03920717dfb492c7b011b070a34656e2b1b6256d
Signed-off-by: Gopireddy Arunteja Reddy <quic_garuntej@quicinc.com>