lib: sbi: Simplify parameters of sbi_illegal_insn_handler()

The struct sbi_trap_context already has the information needed by
sbi_illegal_insn_handler() so directly pass struct sbi_trap_context
pointer to this function.

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