rsi: Properly initialize data in rsi_sdio_ta_reset

rsi: Properly initialize data in rsi_sdio_ta_reset

When building with -Wuninitialized, Clang warns:

drivers/net/wireless/rsi/rsi_91x_sdio.c:940:43: warning: variable 'data'
is uninitialized when used here [-Wuninitialized]
        put_unaligned_le32(TA_HOLD_THREAD_VALUE, data);
                                                 ^~~~
drivers/net/wireless/rsi/rsi_91x_sdio.c:930:10: note: initialize the
variable 'data' to silence this warning
        u8 *data;
                ^
                 = NULL
1 warning generated.

Using Clang's suggestion of initializing data to NULL wouldn't work out
because data will be dereferenced by put_unaligned_le32. Use kzalloc to
properly initialize data, which matches a couple of other places in this
driver.

Fixes: e5a1ecc97e5f ("rsi: add firmware loading for 9116 device")
Link: https://github.com/ClangBuiltLinux/linux/issues/464
Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>