docs: tegra194-hte.rst: don't include gpiolib.c twice

All extern functions of drivers/gpio/gpiolib.c are already
inside the Kernel documentation, as driver-api/gpio/index.rst
already includes it.

Placing a kernel-doc here will only cause mess, as the same symbol
will be placed on two parts of the document, causing breakages
in cross-references.

So, instead, add a cross-reference there.

This solves those Sphinx 3.1+ warnings:
    .../Documentation/driver-api/hte/tegra194-hte:28: ./drivers/gpio/gpiolib.c:2464: WARNING: Duplicate C declaration, also defined at driver-api/gpio/index:2464.
    .../Documentation/driver-api/hte/tegra194-hte:28: ./drivers/gpio/gpiolib.c:2493: WARNING: Duplicate C declaration, also defined at driver-api/gpio/index:2493.
    .../Documentation/driver-api/hte/tegra194-hte.rst:2464: WARNING: Duplicate C declaration, also defined at driver-api/gpio/index:2464.
    .../Documentation/driver-api/hte/tegra194-hte.rst:2464: WARNING: Duplicate C declaration, also defined at driver-api/gpio/index:2464.
    .../Documentation/driver-api/hte/tegra194-hte.rst:2464: WARNING: Duplicate C declaration, also defined at driver-api/gpio/index:2464.
    .../Documentation/driver-api/hte/tegra194-hte.rst:2493: WARNING: Duplicate C declaration, also defined at driver-api/gpio/index:2493.
    .../Documentation/driver-api/hte/tegra194-hte.rst:2493: WARNING: Duplicate C declaration, also defined at driver-api/gpio/index:2493.
    .../Documentation/driver-api/hte/tegra194-hte.rst:2493: WARNING: Duplicate C declaration, also defined at driver-api/gpio/index:2493.
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>
Link: https://lore.kernel.org/r/de81b472f552bd651f140f0aa779a29652fffa62.1656759989.git.mchehab@kernel.orgAcked-by: Dipen Patel <dipenp@nvidia.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Documentation/driver-api/hte/tegra194-hte.rst

@@ -25,8 +25,7 @@ and userspace consumers. The kernel space consumers can directly talk to HTE
 subsystem while userspace consumers timestamp requests go through GPIOLIB CDEV
 framework to HTE subsystem.
 
-.. kernel-doc:: drivers/gpio/gpiolib.c
-   :functions: gpiod_enable_hw_timestamp_ns gpiod_disable_hw_timestamp_ns
+See gpiod_enable_hw_timestamp_ns() and gpiod_disable_hw_timestamp_ns().
 
 For userspace consumers, GPIO_V2_LINE_FLAG_EVENT_CLOCK_HTE flag must be
 specified during IOCTL calls. Refer to ``tools/gpio/gpio-event-mon.c``, which