[vs]: Update swiotlb buffer size to support multi-asic VS platform. (#…

…6674)

Current mutli-asic vs hwsku consists of 6 asics with each asic having 32 interfaces.
When bringing this up, below issue was seen:
When all 32 interfaces in each namespace (sonic interfaces and linux interface) is set to 9100 mtu, DMA error is seen "DMA: Out of SW-IOMMU space for 4096 bytes at device 0000:06:03.0" which can be fixed by updating swiotlb=65536 in /host/grub/grub.cfg .

Signed-off-by: SuvarnaMeenakshi <sumeenak@microsoft.com>

device/virtual/x86_64-kvm_x86_64-r0/installer.conf

@@ -0,0 +1 @@
+ONIE_PLATFORM_EXTRA_CMDLINE_LINUX="swiotlb=65536"