ext4: delete redundant calculations in ext4_mb_get_buddy_page_lock()

'blocks_per_page' is always 1 after 'if (blocks_per_page >= 2)',
'pnum' and 'block' are equal in this case.

Signed-off-by: Gou Hao <gouhao@uniontech.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20231024035215.29474-1-gouhao@uniontech.com


Signed-off-by: Theodore Ts'o <tytso@mit.edu>