RISC-V: remove deprecate pic code model macro

RISC-V: remove deprecate pic code model macro

Came across this deprecated symbol when looking around for
-mexplicit-relocs handling in code

Signed-off-by: Vineet Gupta <vineetg@rivosinc.com>
gcc/ChangeLog:

	* config/riscv/riscv-c.cc (riscv_cpu_cpp_builtins):
	Remove __riscv_cmodel_pic, that deprecated in last version.

gcc/testsuite/ChangeLog:

	* gcc.target/riscv/predef-1.c: Remove __riscv_cmodel_pic check.
	* gcc.target/riscv/predef-2.c: Ditto.
	* gcc.target/riscv/predef-3.c: Ditto.
	* gcc.target/riscv/predef-4.c: Ditto.
	* gcc.target/riscv/predef-5.c: Ditto.
	* gcc.target/riscv/predef-6.c: Ditto.
	* gcc.target/riscv/predef-7.c: Ditto.
	* gcc.target/riscv/predef-8.c: Ditto.