powerpc/xmon: Fix display of SPRs

Convert 0.16x to 0.16lx. Otherwise we lose the top 8 nibbles and
effectively print only the last 32 bits.

Fixes: 1846193b

 ("powerpc/xmon: Dump ISA 2.06 SPRs")
Signed-off-by: Balbir Singh <bsingharora@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>