cpufreq/amd-pstate: Fix amd_pstate mode switch on shared memory systems

cpufreq/amd-pstate: Fix amd_pstate mode switch on shared memory systems

While switching the driver mode between active and passive, Collaborative
Processor Performance Control (CPPC) is disabled in
amd_pstate_unregister_driver(). But, it is not enabled back while registering
the new driver (passive or active). This leads to the new driver mode not
working correctly, so enable it back in amd_pstate_register_driver().

Fixes: 3ca7bc818d8c ("cpufreq: amd-pstate: Add guided mode control support via sysfs")
Signed-off-by: Dhananjay Ugwekar <Dhananjay.Ugwekar@amd.com>
Reviewed-by: Mario Limonciello <mario.limonciello@amd.com>
Link: https://lore.kernel.org/r/20241004122303.94283-1-Dhananjay.Ugwekar@amd.com
Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>