drm/amd/pm: correct table_clk_vlt memory size due to replacing one-element array with flexible-array in struct phm_clock_voltage_dependency_table

Add 1 to the size passed to kzalloc after replacing one-element array.

There is a regular need in the kernel to provide a way to declare having
a dynamically sized set of trailing elements in a structure. Kernel code
should always use “flexible array members”[1] for these cases. The older
style of one-element or zero-length arrays should no longer be used[2].

Refactor the code according to the use of a flexible-array member in
struct phm_ppt_v1_mm_clock_voltage_dependency_table, instead of a
one-element array, and use the struct_size() helper to calculate the
size for the allocation.

[1] https://en.wikipedia.org/wiki/Flexible_array_member
[2] https://www.kernel.org/doc/html/v5.9-rc1/process/deprecated.html#zero-length-and-one-element-arraysSigned-off-by: Mengbing Wang <mengbing.wang@amd.com>
Reviewed-by: Evan Quan <evan.quan@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>