oem_ibm: bios : change the default value of pvm_stop_at_standby

IBM legacy behaviour is to boot to runtime by default, so changing
this attribute default value to align with the legacy designs.

Signed-off-by: Manojkiran Eda <manojkiran.eda@gmail.com>
Change-Id: I26873e3574dc37554b090fce32f047e5aebe0a6f