OvmfPkg/RiscVVirt: Fix issues in VarStore Blockmap config

The block size configuration of Blockmap does not match that in Qemu
VirtNorFlash, which causes variable data to be written into FtwWorkBlock
by mistake, resulting in data loss during reboot. Fix it and update
new checksum value.

Signed-off-by: Qingyu Shang <2931013282@sjtu.edu.cn>
Reviewed-by: Sunil V L <sunilvl@ventanamicro.com>

OvmfPkg/RiscVVirt/VarStore.fdf.inc

@@ -30,9 +30,9 @@ DATA = {
   # Signature "_FVH"       # Attributes
   0x5f, 0x46, 0x56, 0x48, 0xff, 0xfe, 0x04, 0x00,
   # HeaderLength # CheckSum # ExtHeaderOffset #Reserved #Revision
-  0x48, 0x00, 0x2F, 0xF1, 0x00, 0x00, 0x00, 0x02,
-  # Blockmap[0]: 0x20 Blocks * 0x1000 Bytes / Block
-  0x00, 0x08, 0x00, 0x00, 0x00, 0x10, 0x00, 0x00,
+  0x48, 0x00, 0x28, 0x09, 0x00, 0x00, 0x00, 0x02,
+  # Blockmap[0]: 0x3 Blocks * 0x40000 Bytes / Block
+  0x3, 0x00, 0x00, 0x00, 0x00, 0x00, 0x04, 0x00,
   # Blockmap[1]: End
   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
   ## This is the VARIABLE_STORE_HEADER