riscv: Add norvc after .option arch in runtime const

.option arch clobbers .option norvc. Prevent gas from emitting
compressed instructions in the runtime const alternative blocks by
setting .option norvc after .option arch. This issue starts appearing on
gcc 15, which adds zca to the march.

Reported by: Klara Modin <klarasmodin@gmail.com>
Signed-off-by: Charlie Jenkins <charlie@rivosinc.com>
Fixes: a44fb57 ("riscv: Add runtime constant support")
Closes: https://lore.kernel.org/all/cc8f3525-20b7-445b-877b-2add28a160a2@gmail.com/
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20250331-fix_runtime_const_norvc-v1-1-89bc62687ab8@rivosinc.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

Author: charlie-rivos

arch/riscv/include/asm/runtime-const.h

@@ -56,6 +56,7 @@
 #define RISCV_RUNTIME_CONST_64_ZBA				\
 	".option push\n\t"					\
 	".option arch,+zba\n\t"					\
+	".option norvc\n\t"					\
 	"slli	%[__tmp],%[__tmp],32\n\t"			\
 	"add.uw %[__ret],%[__ret],%[__tmp]\n\t"			\
 	"nop\n\t"						\
@@ -65,6 +66,7 @@
 #define RISCV_RUNTIME_CONST_64_ZBKB				\
 	".option push\n\t"					\
 	".option arch,+zbkb\n\t"				\
+	".option norvc\n\t"					\
 	"pack	%[__ret],%[__ret],%[__tmp]\n\t"			\
 	"nop\n\t"						\
 	"nop\n\t"						\