parisc: Fix unaligned-access crash in bootloader

Kernel v5.14 has various changes to optimize unaligned memory accesses,
e.g. commit 0652035 ("asm-generic: unaligned: remove byteshift helpers").

Those changes triggered an unalignment-exception and thus crashed the
bootloader on parisc because the unaligned "output_len" variable now suddenly
was read word-wise while it was read byte-wise in the past.

Fix this issue by declaring the external output_len variable as char which then
forces the compiler to generate byte-accesses.

Signed-off-by: Helge Deller <deller@gmx.de>
Cc: Arnd Bergmann <arnd@kernel.org>
Cc: John David Anglin <dave.anglin@bell.net>
Bug: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102162
Fixes: 8c031ba ("parisc: Unbreak bootloader due to gcc-7 optimizations")
Fixes: 0652035 ("asm-generic: unaligned: remove byteshift helpers")
Cc: <stable@vger.kernel.org> # v5.14+

arch/parisc/boot/compressed/misc.c

@@ -26,7 +26,7 @@
 extern char input_data[];
 extern int input_len;
 /* output_len is inserted by the linker possibly at an unaligned address */
-extern __le32 output_len __aligned(1);
+extern char output_len;
 extern char _text, _end;
 extern char _bss, _ebss;
 extern char _startcode_end;