drm/amdgpu/powerplay/vega10: allow undervolting in p7

The vega10_odn_update_soc_table() function does not allow the SCLK
dependent voltage to be set for power-state 7 to a value below the default
in pptable. Change the for-loop condition to allow undervolting in the
highest state.

Bug: https://bugzilla.kernel.org/show_bug.cgi?id=205277


Signed-off-by: Pelle van Gils <pelle@vangils.xyz>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org