fastbootd: reduce USB buffer size to 16K

Some USB controllers can only support transfers upto 16K.

Bug: 133208811
Test: fastboot flashall
Change-Id: Ic025bdd8e7a6cf2634fc24524fd189e0cc9efbb5
Merged-In: Ic025bdd8e7a6cf2634fc24524fd189e0cc9efbb5
(cherry picked from commit d747dba9c0fd5bb81e4b616cfb562a10c64b9e54)
1 file changed