README: Update supported architecture list

This commit updates the list of supported architectures in the README
to include the recently added architectures.

Signed-off-by: Stephanos Ioannidis <root@stephanos.io>

Author: stephanosio

README.md

@@ -12,8 +12,9 @@ The toolchains for the following target architectures are supported:
 - MIPS (32-bit and 64-bit)
 - Nios II
 - RISC-V (32-bit and 64-bit; RV32I, RV32E, RV64I)
+- SPARC (32-bit and 64-bit; SPARC V8, SPARC V9)
 - x86 (32-bit and 64-bit)
-- Xtensa (sample_controller, intel_apl_adsp, intel_s1000,
+- Xtensa (sample_controller, intel_ace15_mtpm, intel_tgl_adsp,
   nxp_imx_adsp, nxp_imx8m_adsp, espressif_esp32, espressif_esp32s2,
   espressif_esp32s3)