s390/hmcdrv: fix Kconfig "its" grammar

Use the possessive "its" instead of the contraction "it's"
where appropriate.

Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Alexander Gordeev <agordeev@linux.ibm.com>
Cc: linux-s390@vger.kernel.org
Link: https://lore.kernel.org/r/20220715020010.12678-1-rdunlap@infradead.org


Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>