mem-cache: Refactor the cache recvTimingReq function

mem-cache: Refactor the cache recvTimingReq function

The recvTimingReq function in the cache handles timing requests. Over
time, recvTimingReq has grown in complexity and code size. This change
factors out some of its functionality in two separate functions. The
new functions handle timing requests that hit and timing requests that
miss separately.

Change-Id: I09902d648d7272f0f9ec2851fa6376f7305ba418
Reviewed-on: https://gem5-review.googlesource.com/10424
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Reviewed-by: Daniel Carvalho <odanrc@yahoo.com.br>
Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com>