meson: map mipsel TARGET_ARCH to mips for the cross file

Meson uses 'mips' for both big- and little-endian MIPS machines, so map mipsel
to mips.

(From OE-Core rev: 23734432a24da77aa838ad4bdcbcc294cde08348)

Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/classes/meson.bbclass

@@ -52,6 +52,8 @@ def meson_cpu_family(var, d):
     arch = d.getVar(var)
     if arch == 'powerpc':
         return 'ppc'
+    if arch == 'mipsel':
+        return 'mips'
     elif re.match(r"i[3-6]86", arch):
         return "x86"
     else: