ACPI: RISC-V: Fix FFH_CPPC_CSR error handling

ACPI: RISC-V: Fix FFH_CPPC_CSR error handling

The cppc_ffh_csr_read() and cppc_ffh_csr_write() returns Linux error
code in "data->ret.error" so cpc_read_ffh() and cpc_write_ffh() must
not use sbi_err_map_linux_errno() for FFH_CPPC_CSR.

Fixes: 30f3ffbee86b ("ACPI: RISC-V: Add CPPC driver")
Signed-off-by: Anup Patel <apatel@ventanamicro.com>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Reviewed-by: Troy Mitchell <troy.mitchell@linux.dev>
Reviewed-by: Sunil V L <sunilvl@ventanamicro.com>
Reviewed-by: Nutty Liu <nutty.liu@hotmail.com>
Reviewed-by: Atish Patra <atishp@rivosinc.com>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20250818143600.894385-2-apatel@ventanamicro.com
Signed-off-by: Paul Walmsley <pjw@kernel.org>