C2SoftOpusEnc: Fix integer overflows leading to crash by changing data type

Bug: 211910627

Test: POC in bug descriptions
Test: atest VtsHalMediaC2V1_0TargetAudioEncTest
Test: atest CtsMediaTestCases:EncoderTest

(cherry picked from commit d6ec069ca392aeef135c6671fc9701485bd1c60c)
Merged-In: I72fee83ae27d3f446b1584fd4fd047e93a0a01d9

Change-Id: Ieb623453068b7e0babc14a6ae688a975e63bbfd0