powerpc/8xx: Remove left-over instruction and comments in DataStoreTLBMiss handler

powerpc/8xx: Remove left-over instruction and comments in DataStoreTLBMiss handler

Commit ac9f97ff8b32 ("powerpc/8xx: Inconditionally use task PGDIR in
DTLB misses") removed the test that needed the valeur in SPRN_EPN but
failed to remove the read.

Remove it.

And remove related comments, including the very same comment
in InstructionTLBMiss that should have been removed by
commit 33c527522f39 ("powerpc/8xx: Inconditionally use task PGDIR in
ITLB misses").

Also update the comment about absence of a second level table which
has been handled implicitely since commit 5ddb75cee5af ("powerpc/8xx:
remove tests on PGDIR entry validity").

Fixes: ac9f97ff8b32 ("powerpc/8xx: Inconditionally use task PGDIR in DTLB misses")
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Madhavan Srinivasan <maddy@linux.ibm.com>
Link: https://patch.msgid.link/5811c8d1d6187f280ad140d6c0ad6010e41eeaeb.1755361995.git.christophe.leroy@csgroup.eu