fix(ppc): avoid using static TCG variables

[amaanq]

Problem

A lot of variables in qemu/target/ppc/translate.c use global TCG variables, which is unexpected as these variables should be a part of the instance-specific TCG context.

Solution

In this PR, I've moved these global PPC TCG variables to the TCGContext struct.

[wtdcode]

CI fails =)

[amaanq]

The android CI failure is pretty weird..