ath6kl: Fix SDIO error path

sdio_release_host() would be called twice if sdio_set_block_size()
fails for some reason, which would result in the following warning.

WARNING: at /home/sujith/dev/wireless-testing/drivers/mmc/core/core.c:828 mmc_release_host+0x42/0x50 [mmc_core]()

Call Trace:
[<ffffffff81064fdf>] warn_slowpath_common+0x7f/0xc0
[<ffffffff8106503a>] warn_slowpath_null+0x1a/0x20
[<ffffffffa03beb42>] mmc_release_host+0x42/0x50 [mmc_core]
[<ffffffffa03c917e>] sdio_release_host+0x1e/0x30 [mmc_core]
[<ffffffffa053fac7>] ath6kl_sdio_config+0xc7/0x110 [ath6kl_sdio]
[<ffffffffa053fd2c>] ath6kl_sdio_probe+0x21c/0x320 [ath6kl_sdio]
[<ffffffffa03beb2a>] ? mmc_release_host+0x2a/0x50 [mmc_core]
[<ffffffffa03c7d2a>] sdio_bus_probe+0xfa/0x130 [mmc_core]
[<ffffffff813015ae>] driver_probe_device+0x7e/0x1b0
[<ffffffff8130178b>] __driver_attach+0xab/0xb0
[<ffffffff813016e0>] ? driver_probe_device+0x1b0/0x1b0
[<ffffffff813016e0>] ? driver_probe_device+0x1b0/0x1b0
[<ffffffff81300504>] bus_for_each_dev+0x64/0xa0
[<ffffffff8130123e>] driver_attach+0x1e/0x20
[<ffffffff81300e80>] bus_add_driver+0x1b0/0x280
[<ffffffffa0065000>] ? 0xffffffffa0064fff
[<ffffffff81301d06>] driver_register+0x76/0x140
[<ffffffffa0065000>] ? 0xffffffffa0064fff
[<ffffffffa03c7b71>] sdio_register_driver+0x21/0x30 [mmc_core]
[<ffffffffa0065012>] ath6kl_sdio_init+0x12/0x35 [ath6kl_sdio]
[<ffffffff81002042>] do_one_initcall+0x42/0x180
[<ffffffff810b025f>] sys_init_module+0x8f/0x200
[<ffffffff81425ac2>] system_call_fastpath+0x16/0x1b

Signed-off-by: Sujith Manoharan <c_manoha@qca.qualcomm.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>