spi_qsd: Remove check for internal loopback

During multiple transfers,  currently SPI
driver imposes check for read/write length,
If read/write length is greater than  FIFO size
the  transaction are failing due to this check.
This patch removes this check to successfully
transfer the data during  multiple transfers of
size greater than FIFO size.

CRs-Fixed: 592431
Change-Id: I5e24744155d585811a280a213f8d7f298027cd5b
Signed-off-by: Sana Venkat Raju <c_vsana@codeaurora.org>