partition: fix rootfs GUID in the RB1 partition conf file (#830)

As reported on qualcomm-linux/qcom-ptool#9,
the GUID used for rootfs is incorrectly. It was wrongly inherited from
the original partition XML file of an Android build, and the GUID which
was used corresponds to what Android uses for userdata partition.

This changes sets the correct GUID
(b921b045-1df0-41c3-af44-4c6f280d3fae) for Root Partition (64-bit
ARM/AArch64).

Author: lumag

recipes-bsp/partition/files/qcm2290-partitions.conf

@@ -94,4 +94,4 @@
 --partition --name=fsg --size=2048KB --type-guid=638FF8E2-22C9-E33B-8F5D-0E81686A68CB
 --partition --name=fsc --size=128KB --type-guid=57B90A16-22C9-E33B-8F5D-0E81686A68CB
 --partition --name=efi --size=524288KB --type-guid=C12A7328-F81F-11D2-BA4B-00A0C93EC93B --filename=efi.bin
---partition --name=rootfs --size=9960572KB --type-guid=1B81E7E6-F50D-419B-A739-2AEEF8DA3335 --filename=rootfs.img
+--partition --name=rootfs --size=9960572KB --type-guid=B921B045-1DF0-41C3-AF44-4C6F280D3FAE --filename=rootfs.img