spi: zynqmp: gqspi: update function prototypes

This patch updates following functions:

a) zynqmp_gqspi_selectflash():
- Renamed this function name to zynqmp_gqspi_selectslave()
- Updated input parameter names as well
- Added warning messages for the default case of switch statements
- Updated respective function calls

b) zynqmp_qspi_selectspimode():
- Updated signature to accept pointer of the type struct zynqmp_qspi
- Added warning message for the default case of switch statement
- Updated respective function calls

c) zynqmp_qspi_copy_read_data():
- Changed data type of parameter 'data' to ulong
- Removed typecasting in memcpy() call

Signed-off-by: Ranjit Waghmode <ranjit.waghmode@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>