[S390] dcssblk: revert devt conversion
[S390] dcssblk: revert devt conversion

git commit f331c0296f2a9fee0d396a70598b954062603015 changed users of
->first_minor to devt. This broke device handling in dcssblk, so that
no additional devices could be added after the first one.

This patch reverts the devt conversion to the previous ->first_minor
handling.

Signed-off-by: Gerald Schaefer <7a67bf9a8691f9f1ca8ce9577e14c37413ea5f58@de.ibm.com>
Signed-off-by: Martin Schwidefsky <52616596d8f5df0d597e85ab515377f92f939c68@de.ibm.com>

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