nvme-fc: fix the fc_appid_store return value

This fixes an upstream regression in the user interface to the VMID functionality, caused by code refactoring that combined 2 functions. In doing so, the "count" value returned by the sysfs write was not correct for the common case of a terminating \n that is removed by the parsing.

Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2113035 Upstream Status: From upstream git://git.infradead.org/nvme.git branch "nvme-5.20" Tested-by: Tested by Muneendra @ Broadcom/BSN Signed-off-by: Ewan D. Milne emilne@redhat.com