powerpc64/bpf: Convert some of the uses of PPC_BPF_[LL|STL] to PPC_BPF_[LD|STD]

powerpc64/bpf: Convert some of the uses of PPC_BPF_[LL|STL] to PPC_BPF_[LD|STD]

PPC_BPF_[LL|STL] are macros meant for scenarios where we may have to
deal with a non-word aligned offset. Limit their usage to only those
scenarios by converting the rest to just use PPC_BPF_[LD|STD].

Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/0eb472428165a307f6fdaf22b0c33cbf13a9a635.1644834730.git.naveen.n.rao@linux.vnet.ibm.com