drm/i915/display: Consider fractional vdsc bpp while computing m_n values

MTL+ supports fractional compressed bits_per_pixel, with precision of
1/16. This compressed bpp is stored in U6.4 format.
Accommodate this precision while computing m_n values.

v1:
Replace the computation of 'data_clock' with 'data_clock =
DIV_ROUND_UP(data_clock, 16).' (Sui Jingfeng).

v2:
Rebase and pass bits_per_pixel in U6.4 format.

Signed-off-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
Signed-off-by: Mitul Golani <mitulkumar.ajitkumar.golani@intel.com>
Reviewed-by: Suraj Kandpal <suraj.kandpal@intel.com>
Reviewed-by: Sui Jingfeng <suijingfeng@loongson.cn>
Link: https://patchwork.freedesktop.org/patch/msgid/20231110101020.4067342-4-ankit.k.nautiyal@intel.com