cpufreq/amd-pstate: Make amd_pstate_get_mode_string() never return NULL

amd_pstate_get_mode_string() is only used by amd-pstate-ut.  Set the
failure path to use AMD_PSTATE_UNDEFINED ("undefined") to avoid showing
"(null)" as a string when running test suite.

Reviewed-by: Gautham R. Shenoy <gautham.shenoy@amd.com>
Signed-off-by: Mario Limonciello (AMD) <superm1@kernel.org>
This commit is contained in:
Mario Limonciello (AMD) 2025-10-09 11:17:53 -05:00
commit baf106f3a7