soc/mediatek: Don't scan SRAM for winstream in mtk_adsp_load.py

For the same reason that this script can't zero the SRAM region (it
spontaneously reboots my 8186 device) we can't scan the SRAM for the
winstream header.  It's never there anyway, it lives in .rodata.

This is likely a hardware bug, but as it's an older platform and this
is test code it's probably best to just keep it as a workaround.

Signed-off-by: Andy Ross <andyross@google.com>

soc/mediatek/mt8xxx/mtk_adsp_load.py

@@ -276,7 +276,7 @@ class Winstream:
 def find_winstream(maps):
     magic = b'\x74\x5f\x6a\xd0\x79\xe2\x4f\x00\xcd\xb8\xbd\xf9'
     for m in maps:
-        if "ram" in m:
+        if "dram" in m:
             magoff = maps[m].find(magic)
             if magoff >= 0:
                 addr = le4(maps[m][magoff + 12 : magoff + 16])