drm/radeon/ci_dpm: Remove needless NULL checks of dpm tables

This patch removes useless NULL pointer checks in functions like
ci_set_private_data_variables_based_on_pptable() and
ci_setup_default_dpm_tables().

The pointers in question are initialized as addresses to existing
structures such as rdev->pm.dpm.dyn_state.vddc_dependency_on_sclk by
utilizing & operator and therefore are not in danger of being NULL.

Fix this by removing extra checks thus cleaning the code a tiny bit.

Found by Linux Verification Center (linuxtesting.org) with static
analysis tool SVACE.

Fixes: cc8dbbb4 ("drm/radeon: add dpm support for CI dGPUs (v2)")
Signed-off-by: Nikita Zhandarovich <n.zhandarovich@fintech.ru>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>