[media] s5p-mfc: Rename BANK1/2 to BANK_L/R to better match documentation

Documentation for MFC hardware still uses 'left' and 'right' names for
the memory channel/banks, so replace BANK1/2 defines with more appropriate
BANK_L/R names.

Suggested-by: Shuah Khan <shuahkhan@gmail.com>
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>