microblaze: Fix some typos in comment

Replace 'the the' with 'like the' in the comment.
Replace 'an' with 'a'.

Signed-off-by: Slark Xiao <slark_xiao@163.com>
Signed-off-by: Michal Simek <michal.simek@amd.com>
Link: https://lore.kernel.org/r/20220721071520.48384-1-slark_xiao@163.com