lib: sbi: Pass trap context pointer to sbi_ecall_handler()

To be consistent with other trap handlers, pass trap context pointer
to sbi_ecall_handler().

Signed-off-by: Anup Patel <apatel@ventanamicro.com>
Reviewed-by: Samuel Holland <samuel.holland@sifive.com>
Tested-by: Samuel Holland <samuel.holland@sifive.com>
Reviewed-by: Clément Léger <cleger@rivosinc.com>