staging: axis-fifo: Use sysfs_emit()

sysfs_read() is anly called from _show() functions declared by
DEVICE_ATTR_RW().

Using sysfs_emit() is the preferred style and here, it saves a useless
copy and a temporary buffer in the stack.

Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Link: https://lore.kernel.org/r/588327734f374b5f5cb5c4d5725d884fdc83663e.1707654406.git.christophe.jaillet@wanadoo.fr


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>