V4L/DVB (3381): Fix compilation with Alpha

- BOOT_SIZE name is also used at alpha and were breaking
compiling with allyesconfig.
- All BOOT_* renamed to AV7110_BOOT* to fix and keep names
with the same style.
Thanks to Andrew Morton for pointing this.

Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>