Revert "amex/nvram.c: Relax file sharing mode"

This reverts commit 9b47b51bf2b83d7d5a242e38ea6b41b120371e80.

amex/nvram.c

@@ -21,25 +21,10 @@ HRESULT nvram_open_file(HANDLE *out, const wchar_t *path, size_t size)
 
     *out = NULL;
 
-    /* This is somewhat sloppy: allow multiple processes to open the backing
-       store simultaneously. Multiple processes don't actually need to open
-       the backing store simultaneously, but it allows use to reuse the same
-       chunihook.dll for both chuniApp.exe and aimeReaderHost.exe, since a
-       backing store fd gets opened during process init and subsequentely
-       re-used for all device open operations on that NVRAM.
-
-       We could defer the file open until it is actually needed instead, but
-       this requires some messy locking; naive solutions would be racy or would
-       effectively block all but one thread at a time in the process from
-       performing any I/O.
-
-       Hopefully some day Chunithm will move to the new amdaemon-based system
-       architecture. */
-
     file = CreateFileW(
             path,
             GENERIC_READ | GENERIC_WRITE,
-            FILE_SHARE_READ | FILE_SHARE_WRITE,
+            FILE_SHARE_READ,
             NULL,
             OPEN_ALWAYS,
             FILE_ATTRIBUTE_NORMAL,