util/nvmutil: limit EAGAIN/EINTR retries

set it really high though, so it's still
basically reliably

an EINTR/EAGAIN storm could cause problems
in prw()

Signed-off-by: Leah Rowe <leah@libreboot.org>

util/nvmutil/nvmutil.h

@@ -36,6 +36,10 @@ int fchmod(int fd, mode_t mode);
 #define HAVE_REAL_PREAD_PWRITE 0
 #endif
 
+#ifndef MAX_EAGAIN_RETRIES
+#define MAX_EAGAIN_RETRIES 100000
+#endif
+
 #ifndef LOOP_EAGAIN
 #define LOOP_EAGAIN 1
 #endif