bcma: fix buffer size caused crash in bcma_core_mips_print_irq()

Used buffer wasn't big enough to hold whole strings. Example output of
this function is:
[    0.180892] bcma: bus0: core 0x0800, irq: 2(S)* 3  4  5  6  D  I
[    0.180948] bcma: bus0: core 0x0812, irq: 2(S)  3* 4  5  6  D  I
[    0.180998] bcma: bus0: core 0x082d, irq: 2(S)  3  4* 5  6  D  I
[    0.181046] bcma: bus0: core 0x082c, irq: 2(S)  3  4  5  6  D  I*
which means we need to store up to 24 chars.

Fixes: 758f7e06 ("bcma: Use bcma_debug and not pr_cont in MIPS driver")
Signed-off-by: Rafał Miłecki <rafal@milecki.pl>
Cc: stable@vger.kernel.org # v4.15+
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>