parisc: Ensure page alignment in flush functions

Matthew Wilcox noticed, that if ARCH_HAS_FLUSH_ON_KUNMAP is defined
(which is the case for PA-RISC), __kunmap_local() calls
kunmap_flush_on_unmap(), which may call the parisc flush functions with
a non-page-aligned address and thus the page might not be fully flushed.

This patch ensures that flush_kernel_dcache_page_asm() and
flush_kernel_dcache_page_asm() will always operate on page-aligned
addresses.
Signed-off-by: Helge Deller <deller@gmx.de>
Cc: <stable@vger.kernel.org> # v6.0+

arch/parisc/kernel/pacache.S

@@ -889,6 +889,7 @@ ENDPROC_CFI(flush_icache_page_asm)
 ENTRY_CFI(flush_kernel_dcache_page_asm)
 88:	ldil		L%dcache_stride, %r1
 	ldw		R%dcache_stride(%r1), %r23
+	depi_safe	0, 31,PAGE_SHIFT, %r26	/* Clear any offset bits */
 
 #ifdef CONFIG_64BIT
 	depdi,z		1, 63-PAGE_SHIFT,1, %r25
@@ -925,6 +926,7 @@ ENDPROC_CFI(flush_kernel_dcache_page_asm)
 ENTRY_CFI(purge_kernel_dcache_page_asm)
 88:	ldil		L%dcache_stride, %r1
 	ldw		R%dcache_stride(%r1), %r23
+	depi_safe	0, 31,PAGE_SHIFT, %r26	/* Clear any offset bits */
 
 #ifdef CONFIG_64BIT
 	depdi,z		1, 63-PAGE_SHIFT,1, %r25