cpufreq/amd-pstate: Fix setting EPP in performance mode

cpufreq/amd-pstate: Fix setting EPP in performance mode

EPP 0 is the only supported value in the performance policy.
commit 798c47593cca ("cpufreq/amd-pstate: Add support for platform profile
class") changed this while adding platform profile support to the
dynamic EPP feature, but this actually wasn't necessary since platform
profile writes disable manual EPP writes.

Restore allowing writing EPP of 0 when in performance mode.

Reviewed-by: Marco Scardovi <scardracs@disroot.org>
Tested-by: Marco Scardovi <scardracs@disroot.org>
Reported-by: Stuart Meckle <stuartmeckle@gmail.com>
Closes: https://bugzilla.kernel.org/show_bug.cgi?id=221473
Closes: https://gitlab.freedesktop.org/upower/power-profiles-daemon/-/work_items/190
Fixes: 798c47593cca ("cpufreq/amd-pstate: Add support for platform profile class")
Signed-off-by: Mario Limonciello (AMD) <superm1@kernel.org>