firmware: exynos-acpm: Correct kerneldoc and use typical np argument name

Correct kerneldoc warnings after commit a8dc26a0ec43 ("firmware:
exynos-acpm: introduce devm_acpm_get_by_node()") changed the function
prototype:

exynos-acpm.c:672: warning: Function parameter or struct member 'acpm_np' not described in 'acpm_get_by_node'
exynos-acpm.c:672: warning: expecting prototype for acpm_get_by_phandle(). Prototype was for acpm_get_by_node() instead

While touching the lines, change the name of device_node pointer to
'np' to match convention.

Fixes: a8dc26a0ec43 ("firmware: exynos-acpm: introduce devm_acpm_get_by_node()")
Reported-by: kernel test robot <[e-mail]>
Closes: https://lore.kernel.org/oe-kbuild-all/[e-mail]/
Reviewed-by: Tudor Ambarus <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Krzysztof Kozlowski <[e-mail]>

drivers/firmware/samsung/exynos-acpm.c

···
 }
 
 /**
- * acpm_get_by_phandle() - get the ACPM handle using DT phandle.
- * @dev:        device pointer requesting ACPM handle.
- * @property:   property name containing phandle on ACPM node.
+ * acpm_get_by_node() - get the ACPM handle using node pointer.
+ * @dev:	device pointer requesting ACPM handle.
+ * @np:		ACPM device tree node.
  *
  * Return: pointer to handle on success, ERR_PTR(-errno) otherwise.
  */
 static const struct acpm_handle *acpm_get_by_node(struct device *dev,
-						  struct device_node *acpm_np)
+						  struct device_node *np)
 {
 	struct platform_device *pdev;
 	struct device_link *link;
 	struct acpm_info *acpm;
 
-	pdev = of_find_device_by_node(acpm_np);
+	pdev = of_find_device_by_node(np);
 	if (!pdev)
 		return ERR_PTR(-EPROBE_DEFER);