cifs: fix up get_numpages
cifs: fix up get_numpages

Use DIV_ROUND_UP. Also, PAGE_SIZE is more appropriate here since these
aren't pagecache pages.

Signed-off-by: Jeff Layton <4376fbf8623cd7b7c0232225289bb91cedc0a27f@redhat.com>
Reviewed-by: Pavel Shilovsky <7cbcbfe495bad5f7f26ddc6bf28ecd9f36b2e347@etersoft.ru>

KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas