RISC-V: Fix some code style issue(s) in riscv-c.cc [NFC]

RISC-V: Fix some code style issue(s) in riscv-c.cc [NFC]

Notice some code style issue(s) when add __riscv_v_fixed_vlen, includes:

* Meanless empty line.
* Line greater than 80 chars.
* Indent with 3 space(s).
* Argument unalignment.

gcc/ChangeLog:

	* config/riscv/riscv-c.cc (riscv_ext_version_value): Fix
	code style greater than 80 chars.
	(riscv_cpu_cpp_builtins): Fix useless empty line, indent
	with 3 space(s) and argument unalignment.

Signed-off-by: Pan Li <pan2.li@intel.com>