target/ppc: Remove the function ppc_hash64_set_sdr1()

The function ppc_hash64_set_sdr1 basically checked the htabsize and set an
error if it was too big, otherwise it just stored the value in SPR_SDR1.

Given that the only function which calls ppc_hash64_set_sdr1() is
ppc_store_sdr1(), why not handle the checking in ppc_store_sdr1() to avoid
the extra function call. Note that ppc_store_sdr1() already stores the
value in SPR_SDR1 anyway, so we were doing it twice.

Signed-off-by: Suraj Jitindar Singh <sjitindarsingh@gmail.com>
[dwg: Remove unnecessary error temporary]
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
