tools/power x86_energy_perf_policy: Fix incorrect fopen mode usage

tools/power x86_energy_perf_policy: Fix incorrect fopen mode usage

The fopen_or_die() function was previously hardcoded
to open files in read-only mode ("r"), ignoring the
mode parameter passed to it. This patch corrects
fopen_or_die() to use the provided mode argument,
allowing for flexible file access as intended.

Additionally, the call to fopen_or_die() in
err_on_hypervisor() incorrectly used the mode
"ro", which is not a valid fopen mode. This is
fixed to use the correct "r" mode.

Signed-off-by: Kaushlendra Kumar <kaushlendra.kumar@intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>