target/ppc: Don't gen an SDR1 on POWER9 and rework register creation

target/ppc: Don't gen an SDR1 on POWER9 and rework register creation

POWER9 doesn't have a storage description register 1 (SDR1) which is used
to store the base and size of the hash table. Thus we don't need to
generate this register on the POWER9 cpu model. While we're here, the
register generation code for 970, POWER5+, POWER<7/8/9> in general is a
mess where we call a generic function from a model specific function which
then attempts to call model specific functions, so rework this for
readability.

We update ppc_cpu_dump_state so that "info registers" will only display
the value of sdr1 if the register has been generated.

As mentioned above the register generation for the pcc->init_proc
function for 970, POWER5+, POWER7, POWER8 and POWER9 has been reworked
for improved clarity. Instead of calling init_proc_book3s_64 which then
attempts to generate the correct registers through a mess of if statements,
we remove this function and instead call the appropriate register
generation functions directly. This follows the register generation model
used for earlier cpu models (pre-970) whereby cpu specific registers are
generated directly in the init_proc function and makes it easier to
add/remove specific registers for new cpu models.

Signed-off-by: Suraj Jitindar Singh <sjitindarsingh@gmail.com>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>