In definitions for BranchShortHelperR6 and BranchAndLinkShortHelperR6
are noted many source code lines which are very often repeated or very
similar. These lines of code calcluate offsets and for them this CL
introduces functions CalculateOffset().

TEST=
BUG=

Change-Id: Ia64020efaeab207e72fc00d1dcb5b35a4003f36a
Reviewed-on: https://chromium-review.googlesource.com/574229Reviewed-by: Ivica Bogosavljevic <ivica.bogosavljevic@imgtec.com>
Reviewed-by: Miran Karić <Miran.Karic@imgtec.com>
Commit-Queue: Ivica Bogosavljevic <ivica.bogosavljevic@imgtec.com>
Cr-Commit-Position: refs/heads/master@{#46893}