support/scripts/gen-bootlin-toolchains: remove nios2 toolchain

Nios2 will be removed from Buildroot, so Bootlin toolchains will
no longer provide nios2 toolchain in further releases.

Cc: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Signed-off-by: Romain Naour <romain.naour@smile.fr>
Signed-off-by: Julien Olivain <ju.o@free.fr>

support/scripts/gen-bootlin-toolchains

@@ -118,10 +118,6 @@ arches = {
         'conditions': ['BR2_mips64el', 'BR2_mips_64r6', 'BR2_MIPS_NABI32', '!BR2_MIPS_SOFT_FLOAT'],
         'prefix': 'mips64el',
     },
-    'nios2': {
-        'conditions': ['BR2_nios2'],
-        'prefix': 'nios2',
-    },
     'openrisc': {
         'conditions': ['BR2_or1k'],
         'prefix': 'or1k',