x86/kexec: Fix a comment of swap_pages() assembly

x86/kexec: Fix a comment of swap_pages() assembly

When relocate_kernel() gets called, %rdi holds 'indirection_page' and
%rsi holds 'page_list'.  And %rdi always holds 'indirection_page' when
swap_pages() is called.

Therefore the comment of the first line code of swap_pages()

	movq    %rdi, %rcx      /* Put the page_list in %rcx */

.. isn't correct because it actually moves the 'indirection_page' to
the %rcx.  Fix it.

Signed-off-by: Kai Huang <kai.huang@intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Link: https://lore.kernel.org/all/adafdfb1421c88efce04420fc9a996c0e2ca1b34.1724573384.git.kai.huang@intel.com