gpiolib: fix debugfs newline separators

gpiolib: fix debugfs newline separators

The gpiolib debugfs interface exports a list of all gpio chips in a
system and the state of their pins.

The gpio chip sections are supposed to be separated by a newline
character, but a long-standing bug prevents the separator from
being included when output is generated in multiple sessions, making the
output inconsistent and hard to read.

Make sure to only suppress the newline separator at the beginning of the
file as intended.

Fixes: f9c4a31f6150 ("gpiolib: Use seq_file's iterator interface")
Cc: stable@vger.kernel.org	# 3.7
Cc: Thierry Reding <treding@nvidia.com>
Signed-off-by: Johan Hovold <johan+linaro@kernel.org>
Link: https://lore.kernel.org/r/20241028125000.24051-2-johan+linaro@kernel.org
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>