target-ppc: implement lxvll instruction

target-ppc: implement lxvll instruction

lxvll: Load VSX Vector Left-justified with Length

Little/Big-endian Storage:
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+--+--+
|“T”|“h”|“i”|“s”|“ ”|“i”|“s”|“ ”|“a”|“ ”|“T”|“E”|“S”|“T”|FF|FF|
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+--+--+

Loading 14 bytes to vector (8-bit elements) in BE/LE:
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+--+--+
|“T”|“h”|“i”|“s”|“ ”|“i”|“s”|“ ”|“a”|“ ”|“T”|“E”|“S”|“T”|00|00|
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+--+--+

Signed-off-by: Nikunj A Dadhania <nikunj@linux.vnet.ibm.com>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>