riscv: support building double-float modules

The riscv32 toolchain for GCC-12 provided by kernel.org contains libgcc.a
compiled for double-float. To link to it we have to adjust how we build
U-Boot.

As U-Boot actually does not use floating point at all this should not
make a significant difference for the produced binaries.

Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
Reviewed-by: Rick Chen <rick@andestech.com>
Reviewed-by: Leo Yu-Chi Liang <ycliang@andestech.com>
diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index 32a90b8..8f95781 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -152,6 +152,21 @@
 	  when building U-Boot, which results in compressed instructions in the
 	  U-Boot binary.
 
+config RISCV_ISA_F
+	bool "Standard extension for Single-Precision Floating Point"
+	default y
+	help
+	  Adds "F" to the ISA string passed to the compiler.
+
+config RISCV_ISA_D
+	bool "Standard extension for Double-Precision Floating Point"
+	depends on RISCV_ISA_F
+	default y
+	help
+	  Adds "D" to the ISA string passed to the compiler and changes the
+	  riscv32 ABI from ilp32 to ilp32d and the riscv64 ABI from lp64 to
+	  lp64d.
+
 config RISCV_ISA_A
 	def_bool y