KVM: riscv: selftests: Add commandline option for SBI PMU test

KVM: riscv: selftests: Add commandline option for SBI PMU test

SBI PMU test comprises of multiple tests and user may want to run
only a subset depending on the platform. The most common case would
be to run all to validate all the tests. However, some platform may
not support all events or all ISA extensions.

The commandline option allows user to disable any set of tests if
they want to.

Suggested-by: Andrew Jones <ajones@ventanamicro.com>
Signed-off-by: Atish Patra <atishp@rivosinc.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
Link: https://lore.kernel.org/r/20240420151741.962500-25-atishp@rivosinc.com
Signed-off-by: Anup Patel <anup@brainfault.org>