buffer: fix __bread and __bread_gfp kernel-doc

buffer: fix __bread and __bread_gfp kernel-doc

The extra indentation confused the kernel-doc parser, so remove it.  Fix
some other wording while I'm here, and advise the user they need to call
brelse() on this buffer.

__bread_gfp() isn't used directly by filesystems, but the other wrappers
for it don't have documentation, so document it accordingly.

Link: https://lkml.kernel.org/r/20240416031754.4076917-5-willy@infradead.org
Co-developed-by: Pankaj Raghav <p.raghav@samsung.com>
Signed-off-by: Pankaj Raghav <p.raghav@samsung.com>
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Tested-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>