target/ppc: cpu_init: Move 755 L2 cache SPRs into a function

target/ppc: cpu_init: Move 755 L2 cache SPRs into a function

This is just to have 755-specific registers contained into a function,
intead of leaving them open-coded in init_proc_755. It makes init_proc
easier to read and keeps later patches that touch this code a bit
cleaner.

Signed-off-by: Fabiano Rosas <farosas@linux.ibm.com>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Message-Id: <20220216162426.1885923-16-farosas@linux.ibm.com>
Signed-off-by: Cédric Le Goater <clg@kaod.org>