MAINTAINERS: Collect TI FLASH MEDIA drivers into one section

The current SONY MEMORYSTICK CARD SUPPORT section is pointing to the TI
flash media memorystick driver, which is a bit confusing. Let's make this
more clear by moving this part into TI FLASH MEDIA INTERFACE DRIVER
section, but rename the section to TI FLASH MEDIA MEMORYSTICK/MMC DRIVERS,
as to make it more clear.

Finally, add Alex Dubov to the SONY MEMORYSTICK STANDARD SUPPORT, as I
believe that has been the intention.

Cc: Alex Dubov <oakad@yahoo.com>
Cc: Alex Dubov <alex.dubov@gmail.com>
Cc: Maxim Levitsky <maximlevitsky@gmail.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>