net: hostap: fix function cast warning

gcc -Wextra complains about the function type cast:

drivers/net/wireless/intersil/hostap/hostap_hw.c:3173:48: warning: cast between incompatible function types from ‘void (*)(struct tasklet_struct *)’ to ‘void (*)(long unsigned int)’ [-Wcast-function-type]

Avoid this by just using the regular tasklet_setup() function instead
of the incorrect homegrown version.

Fixes: 7433c969 ("intersil: convert tasklets to use new tasklet_setup() API")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20201026213040.3889546-2-arnd@kernel.org