gfp: gfp_types.h: fix typos & punctuation

Correct typos/spellos and punctutation.

Link: https://lkml.kernel.org/r/20231213043316.10128-1-rdunlap@infradead.org


Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>