This patch adds support for reading nvram on the Raspberry Pi. Either
a dedicated nvram partiton or a file in the dos partition on the SD
card may be used.

--- /n/sources/plan9/sys/src/libauthsrv/readnvram.c	Fri Jul 22 13:25:47 2011
+++ /sys/src/libauthsrv/readnvram.c	Fri Dec  9 09:17:36 2022
@@ -52,6 +52,8 @@
 	"power", "/nvram", 0, sizeof(Nvrsafe),	/* OK for Ucu */
 	"arm", "#F/flash/flash0", 0x100000, sizeof(Nvrsafe),
 	"arm", "#F/flash/flash", 0x100000, sizeof(Nvrsafe),
+	"arm", "#S/sdM0/nvram", 0, sizeof(Nvrsafe),
+	"arm", "#S/sdM0/dos", -1, sizeof(Nvrsafe),	/* OK for Raspberry Pi */
 	"debug", "/tmp/nvram", 0, sizeof(Nvrsafe),
 };