drm/amdgpu: Fix function header names in amdgpu_connectors.c

Align the function headers for `amdgpu_max_hdmi_pixel_clock` and
`amdgpu_connector_dvi_mode_valid` with the function implementations so
they match the expected kdoc style.

Fixes the below:
drivers/gpu/drm/amd/amdgpu/amdgpu_connectors.c:1199: warning: This comment starts with '/**', but isn't a kernel-doc comment. Refer Documentation/doc-guide/kernel-doc.rst
 * Returns the maximum supported HDMI (TMDS) pixel clock in KHz.
drivers/gpu/drm/amd/amdgpu/amdgpu_connectors.c:1212: warning: This comment starts with '/**', but isn't a kernel-doc comment. Refer Documentation/doc-guide/kernel-doc.rst
 * Validates the given display mode on DVI and HDMI connectors.

Fixes: 585b2f68 ("drm/amdgpu: Respect max pixel clock for HDMI and DVI-D (v2)")
Cc: Christian König <christian.koenig@amd.com>
Cc: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Srinivasan Shanmugam <srinivasan.shanmugam@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>