drm/amd/display: Wrap dcn32_override_min_req_memclk() in DC_FP_{START, END}

drm/amd/display: Wrap dcn32_override_min_req_memclk() in DC_FP_{START, END}

[Why]
The dcn32_override_min_req_memclk function is in dcn32_fpu.c, which is
compiled with CC_FLAGS_FPU into FP instructions.  So when we call it we
must use DC_FP_{START,END} to save and restore the FP context, and
prepare the FP unit on architectures like LoongArch where the FP unit
isn't always on.

Reported-by: LiarOnce <liaronce@hotmail.com>
Fixes: ee7be8f3de1c ("drm/amd/display: Limit DCN32 8 channel or less parts to DPM1 for FPO")
Signed-off-by: Xi Ruoyao <xry111@xry111.site>
Reviewed-by: Alex Hung <alex.hung@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>