debugfs: Provide a file creation function that also takes an initial size

Provide a file creation function that also takes an initial size so that the
caller doesn't have to set i_size, thus meaning that we don't have to call
deal with ->d_inode in the callers.

Signed-off-by: David Howells <dhowells@redhat.com>

diff --cc drivers/infiniband/hw/cxgb4/device.c
Simple merge

diff --cc drivers/net/ethernet/chelsio/cxgb4/cxgb4_debugfs.c
Simple merge

diff --cc drivers/scsi/csiostor/csio_init.c
Simple merge

diff --cc drivers/usb/gadget/udc/atmel_usba_udc.c
Simple merge

diff --cc fs/debugfs/inode.c
Simple merge

diff --cc include/linux/debugfs.h
Simple merge