[dif/spi_host] remove redeclaration of init DIF
[dif/spi_host] remove redeclaration of init DIF

The handle initialization DIF was declared twice (once in the autogened
header, and once in the manually implemented header). This removes the
duplicated declaration.

Signed-off-by: Timothy Trippel <77eacc84f9735d3cbb55a271710be269fc3a5818@google.com>

lowRISC/opentitan,lowRISC/opentitan,lowRISC/opentitan,lowRISC/opentitan,lowRISC/opentitan,lowRISC/opentitan