Bug#842161: qemu: Bump seabios dependency

[Hilko Bengen]

Source: qemu
Version: 1:2.7+dfsg-1
Severity: normal

Dear Maintainer,

please bump the seabios dependency to >= 1.9 (or 1.9.3). This should
take care of bugs #840853, #841060 related to a missing
linuxboot_dma.bin file.

Cheers,
-Hilko