KVM: PPC: Book3S HV: XIVE: Fix spelling mistakes

Change 'subsquent' to 'subsequent'.
Change 'accross' to 'across'.

Signed-off-by: Zhang Jiaming <jiaming@nfschina.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20220623102031.15359-1-jiaming@nfschina.com