qup_i2c: turn off the ahb clock conditionally

Each GSBI has QUP-I2C and UART cores which can be
used independently. However, the AHB clock is
shared by these blocks. So we keep it on if the
cores are used independently from different processors.

CRs-Fixed: 387908
Change-Id: I84f96cc6dd4873d96437884d18c911e4cf2bfd51
Signed-off-by: Kiran Gunda <kgunda@codeaurora.org>