media: vidtv: cleanup SDT string identifiers

In order to better test userspace applications, add an encoding
for the strings. The original channel string is also too big.
As we're just playing the first compasses of the 5th Beethoven
Symphony, change the service name to just "Beethoven". Also,
add a provider's name. For such purpose, let's point it to
the Linux media community website.

With such changes, the SDT table now looks more like one got
from a real digital TV channel:

SDT
| table_id         0x42
| section_length      44
| one                 2
| zero                1
| syntax              1
| transport_stream_id 1860
| current_next        1
| version             0
| one2                3
| section_number      0
| last_section_number 0
| network_id          65281
| reserved            255
|\
|- service 0x0880
|   EIT schedule          0
|   EIT present following 0
|   free CA mode          0
|   running status        4
|   descriptor length     27
|        0x48: service_descriptor
|           service type  1
|           provider      'LinuxTV.org'
|           name          'Beethoven'
|_  1 services

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>