drivers/perf: riscv: Fix Platform firmware event data

Platform firmware event data field is allowed to be 62 bits for
Linux as uppper most two bits are reserved to indicate SBI fw or
platform specific firmware events.
However, the event data field is masked as per the hardware raw
event mask which is not correct.

Fix the platform firmware event data field with proper mask.

Fixes: f0c9363d ("perf/riscv-sbi: Add platform specific firmware event handling")

Signed-off-by: Atish Patra <atishp@rivosinc.com>
Link: https://lore.kernel.org/r/20241212-pmu_event_fixes_v2-v2-1-813e8a4f5962@rivosinc.com


Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>