x86/mm: Fix the odd indentation of the pin_page block of do_mmuext_op()

x86/mm: Fix the odd indentation of the pin_page block of do_mmuext_op()

The pin_page block is missing one level of indentation, which makes the
MMUEXT_UNPIN_TABLE case label appear to be outside of the switch statement.

However, the block isn't needed at all if page is declared with switch level
scope.  This allows for the removal of the identical local declarations for
MMUEXT_UNPIN_TABLE, MMUEXT_NEW_USER_BASEPTR and MMUEXT_CLEAR_PAGE.

While making this adjustment, delete one other piece of trailing whitespace.

No functional change.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Wei Liu <wei.liu2@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>