drm/amd/display: fix kernel_fpu_begin/_end() warnings

kernel_fpu_begin/_end() are already called inside dcn20_resource_construct,
and calling kernel_fpu_begin/_end() recursively triggers WARN_ON() when
CONFIG_X86_DEBUG_FPU is enabled.

[  107.060434] WARNING: CPU: 6 PID: 1370 at arch/x86/kernel/fpu/core.c:90 kernel_fpu_begin+0xbd/0xe0
<snip>
[  107.268197] Call Trace:
[  107.270751]  dcn20_patch_bounding_box+0x17/0x100 [amdgpu]
[  107.276204]  init_soc_bounding_box+0x1b3/0x5f0 [amdgpu]
[  107.281536]  ? _cond_resched+0x19/0x30
[  107.285307]  dcn20_resource_construct+0x3a9/0xa90 [amdgpu]
[  107.290957]  ? dcn20_resource_construct+0x3a9/0xa90 [amdgpu]
[  107.296621]  ? __alloc_pages_nodemask+0x16a/0x330
[  107.301476]  ? _cond_resched+0x19/0x30
[  107.305284]  ? kmem_cache_alloc_trace+0x197/0x230
[  107.310063]  ? _cond_resched+0x19/0x30
[  107.313783]  ? kmem_cache_alloc_trace+0x197/0x230
[  107.318691]  dcn20_create_resource_pool+0x42/0x70 [amdgpu]
[  107.324315]  dc_create_resource_pool+0x12d/0x170 [amdgpu]
[  107.329851]  dc_create+0x1b8/0x6a0 [amdgpu]
[  107.334013]  ? kmem_cache_alloc_trace+0x1e2/0x230
[  107.338832]  amdgpu_dm_init+0x13e/0x1c0 [amdgpu]
<snip>
Signed-off-by: Xiaojie Yuan <xiaojie.yuan@amd.com>
Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/dcn20/dcn20_resource.c

@@ -3225,7 +3225,6 @@ void dcn20_update_bounding_box(struct dc *dc, struct _vcs_dpi_soc_bounding_box_s
 
 void dcn20_patch_bounding_box(struct dc *dc, struct _vcs_dpi_soc_bounding_box_st *bb)
 {
-	DC_FP_START();
 	if ((int)(bb->sr_exit_time_us * 1000) != dc->bb_overrides.sr_exit_time_ns
 			&& dc->bb_overrides.sr_exit_time_ns) {
 		bb->sr_exit_time_us = dc->bb_overrides.sr_exit_time_ns / 1000.0;
@@ -3249,7 +3248,6 @@ void dcn20_patch_bounding_box(struct dc *dc, struct _vcs_dpi_soc_bounding_box_st
 		bb->dram_clock_change_latency_us =
 				dc->bb_overrides.dram_clock_change_latency_ns / 1000.0;
 	}
-	DC_FP_END();
 }
 
 static struct _vcs_dpi_soc_bounding_box_st *get_asic_rev_soc_bb(